Phillips v. E.I. DuPont De Nemours & Co. ( 2007 )


Menu:
  •                   FOR PUBLICATION
    UNITED STATES COURT OF APPEALS
    FOR THE NINTH CIRCUIT
    In re: HANFORD NUCLEAR                  
    RESERVATION LITIGATION,
    BARBARA JEAN PHILLIPS,
    Plaintiff,
    and
    WANDA BUCKNER; SHIRLEY                        No. 05-35648
    CARLISLE,
    Plaintiffs-Appellants,          D.C. No.
    CV-91-03015-WFN
    v.
    E.I. DUPONT DE NEMOURS & CO., a
    Delaware corporation; GENERAL
    ELECTRIC CO., a New York
    corporation; UNC NUCLEAR
    INDUSTRIES, INC., a Delaware
    corporation,
    Defendants-Appellees.
    
    9785
    9786    IN RE: HANFORD NUCLEAR RESERVATION LITIGATION
    In re: HANFORD NUCLEAR                  
    RESERVATION LITIGATION,
    BARBARA JEAN PHILLIPS,
    Plaintiff,
    and
    GLORIA HOPE; CLARA REISS;
    GLENDA WINSLOW; KATHRYN J.                    No.05-35651
    GOLDBLOOM, aka Kathryn Janelle
    Goldbloom,                                     D.C. No.
    Plaintiffs-Appellants,       CV-91-03015-WFN
    v.
    E.I. DUPONT DE NEMOURS & CO., a
    Delaware corporation; GENERAL
    ELECTRIC CO., a New York
    corporation; UNC NUCLEAR
    INDUSTRIES, INC., a Delaware
    corporation,
    Defendants-Appellees.
    
    IN RE: HANFORD NUCLEAR RESERVATION LITIGATION   9787
    In re: HANFORD NUCLEAR                  
    RESERVATION LITIGATION,
    BARBARA JEAN PHILLIPS,
    Plaintiff,
    and
    GLORIA HOPE; CLARA REISS;
    GLENDA WINSLOW; WANDA
    BUCKNER; KATHRYN J. VANCAMPEN,
    aka Kathryn Janelle Goldbloom;                No. 05-35678
    SHIRLEY CARLISLE,
    Plaintiffs-Appellees,           D.C. No.
    CV-91-03015-WFN
    v.
    E.I. DUPONT DE NEMOURS & CO., a
    Delaware corporation; GENERAL
    ELECTRIC CO., a New York
    corporation,
    Defendants-Appellants,
    and
    UNC NUCLEAR INDUSTRIES, INC., a
    Delaware corporation,
    Defendant.
    
    9788   IN RE: HANFORD NUCLEAR RESERVATION LITIGATION
    BARBARA JEAN PHILLIPS,                 
    Plaintiff,
    and
    STEVEN STANTON; GLORIA WISE,                 No. 05-35866
    Plaintiffs-Appellees,           D.C. No.
    v.                         CV-91-03015-WFN
    E.I. DUPONT DE NEMOURS & CO.;
    GENERAL ELECTRIC CO.,
    Defendants-Appellants.
    
    IN RE: HANFORD NUCLEAR RESERVATION LITIGATION   9789
    PAMELA DURFEY; PAULENE ECHO             
    HAWK; DOROTHY GEORGE, on their
    own behalf and on behalf of a
    class of similarly situated persons,
    Plaintiffs-Appellants,
    v.
    E. I. DUPONT DE NEMOURS & CO.,
    a Delaware Corporation; GENERAL
    ELECTRIC CO., a New York
    Corporation, UNC NUCLEAR                      No. 05-35892
    INDUSTRIES, INC., a Delaware                   D.C. No.
    Corporation, ATLANTIC RICHFIELD             CV-93-03087-WFN
    COMPANY, ATLANTIC RICHFIELD-
    HANFORD CO., a Washington
    Corporation; ROCKWELL
    INTERNATIONAL CORP., a Delaware
    Corporation; WESTINGHOUSE
    HANFORD CORP., a Delaware
    Corporation; WESTINGHOUSE
    ELECTRIC CORP., a Pennsylvania
    Corporation,
    Defendants-Appellees.
    
    9790    IN RE: HANFORD NUCLEAR RESERVATION LITIGATION
    In re: HANFORD NUCLEAR                  
    RESERVATION LITIGATION,
    PAMELA DURFEY; PAULINE ECHO
    HAWK; DOROTHY GEORGE, on their
    own behalf and on behalf of a
    class of similarly situated persons,
    Plaintiffs-Appellants,
    v.
    E.I. DUPONT DE NEMOURS & CO., a
    Delaware corporation; GENERAL                 No. 05-35895
    ELECTRIC CO., a New York
    corporation; UNC NUCLEAR
           D.C. No.
    CV-91-03015-WFN
    INDUSTRIES, INC., a Delware
    corporation; ATLANTIC RICHFIELD
    COMPANY; ATLANTIC RICHFIELD-
    HANFORD CO., a Washington
    corporation; ROCKWELL
    INTERNATIONAL CORP., a Deleware
    corporation; WESTINGHOUSE
    HANFORD CORPORATION, a Delaware
    corporation; WESTINGHOUSE
    ELECTRIC CORP., a Pennsylvania
    corporation,
    Defendants-Appellees.
    
    IN RE: HANFORD NUCLEAR RESERVATION LITIGATION   9791
    In re: HANFORD NUCLEAR                 
    RESERVATION LITIGATION,
    SHANNON C. RHODES,                           No. 06-35165
    Plaintiff-Appellant,
    v.                            D.C. No.
    CV-91-03015-WFN
    E.I. DUPONT DE NEMOURS & CO., a               OPINION
    Delaware corporation; GENERAL
    ELECTRIC CO., a New York
    corporation,
    Defendants-Appellees.
    
    Appeal from the United States District Court
    for the Eastern District of Washington
    Wm. Fremming Nielsen, Senior Judge, Presiding
    Argued and Submitted
    February 7, 2007—Pasadena, California
    Filed August 14, 2007
    Before: Mary M. Schroeder, Chief Circuit Judge,
    Alfred T. Goodwin and Michael Daly Hawkins,
    Circuit Judges.
    Opinion by Chief Circuit Judge Schroeder
    9796     IN RE: HANFORD NUCLEAR RESERVATION LITIGATION
    COUNSEL
    Peter Nordberg, Berger & Montague, P.C., Philadelphia,
    Pennsylvania; Roy S. Haber, Roy S. Haber, P.C., Eugene,
    Oregon; Daniel Johnson and David Breskin, Short Cressman
    & Burgess, PLLC, Seattle, Washington, for the plaintiffs-
    appellants-appellees.
    Christopher Landau, Kirkland & Ellis, LLP, Washington,
    D.C., for the defendants-appellees-appellants.
    OPINION
    SCHROEDER, Chief Circuit Judge:
    I.   Introduction.
    The origins of this case trace back more than sixty years to
    the height of World War II when the federal government
    solicited Appellants E.I. DuPont de Nemours & Co., General
    Electric, Inc., UNC Nuclear Industries, Inc., Atlantic Rich-
    field Co., and Rockwell International Corp., (collectively
    “Defendants”) to operate the Hanford Nuclear Weapons Res-
    ervation (“Hanford”) in southeastern Washington. The Han-
    ford Reservation was a plutonium-production facility that
    helped make the atomic bomb that dropped on Nagasaki,
    Japan in World War II.
    A regrettable Hanford byproduct was the radioiodine emit-
    ted into the surrounding area. The plaintiffs in this litigation
    are over two thousand residents who now claim that these
    emissions, known as I-131, caused various cancers and other
    life-threatening diseases. The first group of plaintiffs filed a
    complaint in 1990 under the federal statute governing nuclear
    accidents, the Price-Anderson Act (“PAA”), claiming they
    were entitled to damages for injuries arising from a nuclear
    IN RE: HANFORD NUCLEAR RESERVATION LITIGATION        9797
    incident pursuant to 
    42 U.S.C. § 2210
    . The history is dis-
    cussed in our earlier opinions in In re Hanford Nuclear Reser-
    vation Litigation, 
    292 F.3d 1124
     (9th Cir. 2002) (“In re
    Hanford”); and Berg v. E.I. DuPont de Nemours & Co., 
    293 F.3d 1127
     (9th Cir. 2002) (“Berg”). After almost two decades
    of litigation, which already has included two appeals to this
    court, the parties in 2005 agreed to a bellwether trial. The trial
    was designed to produce a verdict that would highlight the
    strengths and weaknesses of the parties’ respective cases and
    thus focused on six plaintiffs (“Plaintiffs”) who were repre-
    sentative of the larger group. The purpose of the trial was to
    promote settlement and bring long-overdue resolution to this
    litigation.
    Before us on appeal is a litany of issues stemming from the
    bellwether trial. A threshhold issue is whether Defendants
    may seek complete immunity under the common law govern-
    ment contractor defense, because they were operating Han-
    ford at the request of the federal government. We hold that the
    defense is inapplicable as a matter of law, because Congress
    enacted the PAA before the courts recognized the government
    contractor defense, and the PAA provides a comprehensive
    liability scheme that precludes Defendants’ reliance on such
    a defense.
    In the alternative, Defendants argue that even if they are
    not immune, they are not strictly liable for any I-131 emis-
    sions, because the amounts of the emissions were within
    federally-authorized levels; the plutonium-production process
    was not an abnormally dangerous activity that would create
    strict liability; and even if it were, Defendants qualify for the
    “public duty” exception to strict liability. The district court
    held that none of Defendants’ contentions were sufficient to
    relieve them of strict liability for the injuries they caused. We
    agree.
    With respect to the trial itself, the district court with admi-
    rable diligence ruled on many issues of first impression. We
    9798     IN RE: HANFORD NUCLEAR RESERVATION LITIGATION
    hold that under Washington law, the district court properly
    instructed the jury that to impose liability, it had to find Han-
    ford was the “but for” cause of Plaintiffs’ diseases and not
    just a contributing cause under the more lenient “substantial
    factor” test. The court also made a host of evidentiary rulings
    that are before us on appeal. We hold that three of these rul-
    ings constitute reversible error with respect to three of the
    Bellwether Plaintiffs.
    There are statute of limitations issues as well. We hold that
    any Hanford Plaintiffs who filed independent suits pending
    class certification lost the benefits of class action tolling, thus
    potentially rendering their suits untimely. Because the record
    before us is incomplete as to the date necessary to measure
    the appropriate tolling period for various plaintiffs, we
    remand the statute of limitations issues to the district court for
    further proceedings.
    Lastly, we hold that the district court properly dismissed
    any medical monitoring claims as not cognizable under the
    PAA. This is consistent with our decision in Berg, 
    293 F.3d 1127
    .
    II.    Background.
    The United States government constructed Hanford during
    World War II to manufacture plutonium for military purposes.
    The facility was a component of the Army Corps of Engi-
    neer’s secret Manhattan Project, with the primary objective of
    developing an atomic bomb. In 1942, the Army Corps began
    hiring civilian contractors to help build and operate the Han-
    ford facility. It first recruited the University of Chicago Met-
    allurgical Laboratory (“Met Lab”) to design the process and
    equipment to produce plutonium. It then solicited E.I. DuPont
    de Nemours & Co. (“DuPont”) to actually run the facility. It
    is apparent the government itself did not have the expertise or
    resources to operate Hanford.
    IN RE: HANFORD NUCLEAR RESERVATION LITIGATION      9799
    DuPont initially refused. The government, however, per-
    sisted and implored DuPont to run the plutonium-production
    facility, because, as the government provided in DuPont’s
    contract, the project was of the “utmost importance” and was
    “necessary in facilitating the prosecution of the war.” DuPont
    eventually acquiesced, stating it would run the facility out of
    patriotic considerations. It accepted only one dollar as pay-
    ment for its services. Several years later, the Hanford facility
    successfully produced the plutonium that was used in 1945 to
    drop the atomic bomb on Nagasaki and effectively end World
    War II. (The bomb dropped on Hiroshima was uranium-
    based, not plutonium-based).
    As part of the plutonium-production process, the Hanford
    facility emitted I-131, a fission byproduct known as radioio-
    dine. I-131 was known at the time to have potential adverse
    health effects on humans. Accordingly, the Met Lab scientists
    set tolerance doses for human exposure. For example, the Met
    Lab determined that the human thyroid should not absorb
    more than one rad per day for those individuals subject to
    continuous exposure in the area. A rad is a measurement of
    the amount of radioiodine absorbed into an organ or tissue.
    On the basis of these safe exposure limit estimates, the Met
    Lab approved a detailed operating procedure that would
    ensure that the plutonium was produced within those emission
    limits. The key to decreasing I-131 emissions was to allow for
    longer cooling times of the uranium slugs used to produce the
    plutonium. This strategy, however, often conflicted with the
    federal government’s orders to increase plutonium produc-
    tion.
    On September 1, 1946, DuPont transferred its duties to
    General Electric (“GE”), which also agreed to earn no profit
    from its work. GE ran the Hanford facility through the Cold
    War. During the period of its operation, GE asked the federal
    government to increase cooling times to allow for lower emis-
    sions of I-131. By this time, Congress had established the
    Atomic Energy Commission (“AEC”), see 42 U.S.C.
    9800    IN RE: HANFORD NUCLEAR RESERVATION LITIGATION
    §§ 2011-2013 (1946), and GE was bound by its determina-
    tions. The AEC denied the request for longer cooling times,
    and GE continued to produce plutonium consistent with gov-
    ernment demands. By the 1950s, however, significant
    improvements were made to the production process, and I-
    131 emission levels dropped.
    In 1987, the United States Department of Energy (“DOE”)
    created the Hanford Environmental Dose Reconstruction Proj-
    ect (“HEDR”), overseen by the Center for Disease Control
    and Prevention. The underlying purpose of the HEDR was to
    estimate and reconstruct all radionuclide emissions from Han-
    ford from 1944 to 1972 in order to ascertain whether neigh-
    boring individuals and animals had been exposed to harmful
    doses of radiation. Of particular concern to the HEDR were
    the estimated doses of I-131 received by the thyroid glands of
    humans, principally through consumption of milk from cows
    that ingested contaminated vegetation on neighboring farms
    and pastures. The HEDR concluded that I-131 emissions
    peaked during the period from 1944 to 1946, when an esti-
    mated 88% of Hanford’s total iodine emissions occurred.
    HEDR explained that in later years, emissions declined
    because of technological advances. In 1990, the Technical
    Steering Panel of HEDR released a report entitled Initial Han-
    ford Radiation Dose Estimates that publicly disclosed for the
    first time that large quantities of radioactive and non-
    radioactive substances had been released from Hanford,
    beginning in the 1940s.
    This disclosure sparked a blaze of litigation. Thousands of
    plaintiffs filed suit pursuant to the Price-Anderson Act, 
    42 U.S.C. § 2210
    (n)(2), which had been amended in 1988 to pro-
    vide exclusive federal jurisdiction over all claims arising from
    a nuclear incident, otherwise known as public liability actions.
    The PAA allowed the plaintiffs to sue private parties, such as
    DuPont, and to consolidate the claims in federal district court.
    
    Id.
     While Congress wanted to ensure that victims of nuclear
    incidents recovered compensation, it also included govern-
    IN RE: HANFORD NUCLEAR RESERVATION LITIGATION       9801
    ment indemnification provisions in the PAA to give private
    parties an incentive to participate in the nuclear industry. See,
    e.g., S. REP. NO. 100-70, at 14 (1988), reprinted in 1988
    U.S.C.C.A.N. 1424, 1425-26.
    The PAA provides that although federal courts have exclu-
    sive and original jurisdiction over claims stemming from
    nuclear incidents, the substantive rules of decision are pro-
    vided by the law of the state in which the nuclear incident
    occurs. See 
    42 U.S.C. § 2014
    (hh). Plaintiffs therefore brought
    tort claims under Washington law, asserting that because
    Defendants were engaged in an abnormally dangerous activ-
    ity, they were strictly liable for any Hanford-caused radiation
    illness.
    On August 6, 1990, a group of plaintiffs filed a joint con-
    solidated complaint in the Eastern District of Washington,
    alleging a class action against Defendants. In 1991, the dis-
    trict court consolidated any and all Hanford-related actions
    pending in various courts, directed preparation of one consoli-
    dated complaint, and designated specific lead counsel for all
    parties. In an order dated September 22, 1994, the district
    court addressed the issue of class certification and decided to
    reserve decision under Federal Rule of Civil Procedure
    23(b)(3) pending further discovery on causation issues.
    Accordingly, pending class certification, the litigation pro-
    ceeded as a consolidated action. Throughout this period, the
    district court entertained a handful of dispositive motions,
    which led to two appeals to this court. In 2002, we heard In
    re Hanford, 
    292 F.3d 1124
    , challenging the district court’s
    dismissal of plaintiffs who could not establish they received
    a “doubling dose” of radiation. We held that Plaintiffs’ claims
    should proceed even if they could not show that Hanford radi-
    ation doubled their risk of illness, and we remanded for trial.
    
    Id. at 1139
    .
    We also heard the appeal in the related case, Berg, 
    293 F.3d 1127
    . The Berg plaintiffs had not yet suffered from any ill-
    9802    IN RE: HANFORD NUCLEAR RESERVATION LITIGATION
    ness, but sued Defendants for medical monitoring. We held
    that medical monitoring claims were not compensable under
    the PAA and upheld the district court’s dismissal of those
    actions with prejudice. 
    Id. at 1133
    .
    After our decisions in In re Hanford and Berg, Judge Wil-
    liam Fremming Nielsen steered the case toward resolution.
    The parties agreed to proceed with a bellwether trial, hoping
    it would reveal the strengths and weaknesses of their respec-
    tive cases and thus pave the way for a settlement. The parties
    eventually agreed on twelve bellwether plaintiffs. Six of these
    plaintiffs had their claims dismissed on dispositive, pre-trial
    motions. The remaining six plaintiffs went to trial in April
    2005.
    The Bellwether Plaintiffs represent plaintiffs who suffer
    from various thyroid diseases they claim were caused by radi-
    ation emanating from Hanford. Plaintiffs Gloria Wise and
    Steven Stanton have thyroid cancer. Plaintiffs Wanda Buck-
    ner, Shirley Carlisle, and Kathryn Goldbloom suffer from
    hypothyroidism, a condition that slows the body’s metabo-
    lism. Hypothyroidism is most frequently caused by Hashimo-
    to’s disease, an illness that Plaintiffs claim was caused by
    Hanford radiation. Plaintiff Shannon Rhodes suffers from
    lung cancer, which her doctors concluded was a form of
    Hurthle cell thyroid cancer that had metastasized from a thy-
    roid lobe previously removed.
    Prior to trial, the Bellwether Plaintiffs made several
    motions to strike Defendants’ affirmative defenses. Defen-
    dants first claimed that the government contractor defense
    insulated them from all liability. The district court, in an
    unpublished 2003 order, struck the defense under Federal
    Rule of Civil Procedure 12(b), holding that the PAA displaced
    any such defense as a matter of law. In a published order, the
    court also ruled that plutonium production at Hanford was an
    abnormally dangerous activity warranting strict liability under
    Washington law. In re Hanford Nuclear Res. Litig., 350 F.
    IN RE: HANFORD NUCLEAR RESERVATION LITIGATION        9803
    Supp. 2d 871, 888 (E.D. Wash. 2004). It then limited the
    issues at trial to causation and damages. 
    Id.
    The primary dispute at trial was whether the amount of
    radiation to which each plaintiff was exposed was sufficient
    to be the cause-in-fact of his or her thyroid disease. There was
    extensive testimony that I-131 radiation causes Hashimoto’s
    disease, a cause of hypothyroidism, and that I-131 can also be
    a contributing factor to thyroid cancer. The testimony
    revealed, however, that to date epidemiological studies can
    establish only that radiation of at least 100 rads is a contribut-
    ing factor to thyroid illness. Some epidemiological studies
    hypothesize that 40 rads might cause Hashimoto’s disease,
    but there are no data beyond that threshold.
    Because many Plaintiffs were not exposed to radiation
    above 40 rads, and no Plaintiff was exposed to radiation
    above 100 rads, Plaintiffs had to present expert testimony that
    scientific extrapolation permitted a finding of causation below
    40 rads. Their primary experts were Dr. Terry Davies, an
    endocrinologist, Dr. Sara Peters, a pathologist, Dr. F. Owen
    Hoffman, a causation expert, and Dr. Colin Hill, a radiation
    cell biologist. Plaintiffs also proffered the expert testimony of
    epidemiologist Dr. A. James Ruttenber, but key parts of his
    testimony relating to causation were excluded.
    After fourteen days of trial and four days of deliberations,
    the jury found in favor of two plaintiffs, Steve Stanton and
    Gloria Wise; the jury hung with respect to one plaintiff, Shan-
    non Rhodes; and it found in favor of Defendants with respect
    to the remaining three plaintiffs, Wanda Buckner, Shirley
    Carlisle, and Kathryn Goldbloom. As damages for prevailing
    plaintiffs, the jury awarded Stanton $227,508 and Wise
    $317,251. Because the jury could not reach a verdict with
    respect to Plaintiff Rhodes, the district court declared a mis-
    trial. Rhodes re-tried her claims in front of a second jury in
    November 2005, and the jury entered a defense verdict on all
    counts.
    9804    IN RE: HANFORD NUCLEAR RESERVATION LITIGATION
    Rhodes, along with the three non-prevailing plaintiffs in the
    first trial, appeal a variety of evidentiary rulings, as well as
    the district court’s jury instruction that under Washington law
    Plaintiffs had to prove “but-for” causation, rather than “sub-
    stantial factor” causation. Defendants appeal the judgments
    entered in favor of the two prevailing plaintiffs, claiming the
    district court erred as a matter of law in striking the govern-
    ment contractor defense. In the alternative, Defendants argue
    that Plaintiffs may not proceed under a strict liability theory,
    because the I-131 emissions were within federally-authorized
    levels. They also contend the plutonium-production process
    was not an abnormally dangerous activity under Washington
    law and, even if it were, that Defendants qualify for the nar-
    row “public duty” exception to strict liability.
    Defendants also contend that prevailing Plaintiff Wise’s
    suit was untimely under Washington’s statute of limitations.
    See Am. Pipe & Constr. Co. v. Utah, 
    414 U.S. 538
     (1974).
    Wise had filed an independent action in 1997, likely beyond
    the statutory period, but Defendants did not invoke American
    Pipe and the district court allowed Wise’s claim to proceed as
    part of the pending class action.
    Apart from the issues relating to the Bellwether Plaintiffs,
    Plaintiffs Pamela Durfey, Paulene Echo Hawk, and Dorothy
    George, who do not yet have symptoms of any thyroid dis-
    ease, sued Defendants for the costs of medical monitoring.
    The district court, following this court’s decision in Berg, 
    293 F.3d at 1132-33
    , held that the PAA precluded any medical
    monitoring claims that were unaccompanied by physical
    injury. Rather than remanding those claims to state court,
    however, the district court held that the PAA bestowed exclu-
    sive jurisdiction in the federal courts for claims arising from
    a nuclear incident, and that therefore the PAA’s provisions
    preempted any state-derived medical monitoring claim.
    Accordingly, it directed entry of final judgment for DuPont
    under Federal Rule of Civil Procedure 54(b). The plaintiffs
    appeal this dismissal.
    IN RE: HANFORD NUCLEAR RESERVATION LITIGATION      9805
    III.   The Government Contractor Defense.
    The overarching issue before us is Defendants’ contention
    that the government contractor defense is available to them as
    a matter of law and that it provides complete immunity from
    liability if its substantive requirements are satisfied. The dis-
    trict court held that the affirmative defense was inapplicable
    as a matter of law because the provisions of the PAA cannot
    be reconciled with the defense and implicitly displace it. We
    review de novo the district court’s conclusion that the affirma-
    tive defense is unavailable, United States v. Griffin, 
    440 F.3d 1138
    , 1143 (9th Cir. 2006), and we reach the same conclu-
    sion.
    [1] The government contractor defense is by now an estab-
    lished component of federal common law, but it was first rec-
    ognized by the Supreme Court less than twenty years ago in
    Boyle v. United Techs. Corp., 
    487 U.S. 500
     (1988). The
    defense is intended to implement and protect the discretionary
    function exception of the Federal Tort Claims Act (“FTCA”),
    
    28 U.S.C. § 2680
    (a), which was enacted after World War II.
    The defense allows a contractor-defendant to receive the ben-
    efits of sovereign immunity when a contractor complies with
    the specifications of a federal government contract. Boyle,
    
    487 U.S. at 511-12
    . As the Court said in Boyle, “[i]t makes
    little sense to insulate the Government against financial liabil-
    ity for the judgment that . . . equipment is necessary when the
    Government produces the equipment itself, but not when it
    contracts for the production.” 
    Id. at 512
    .
    As a threshold matter, we agree with Defendants that the
    government contractor defense applies not only to claims
    challenging the physical design of a military product, but also
    to the process by which such equipment is produced. Accord-
    ingly, a contractor who agrees to operate a production facility
    pursuant to government specifications may qualify for the
    defense.
    9806    IN RE: HANFORD NUCLEAR RESERVATION LITIGATION
    The issue here, however, is whether the PAA preempts reli-
    ance on the common law doctrine, either because the defense
    contradicts the federal statute or because the statute predates
    the defense. Congress is presumed to “legislate against a
    background of common-law adjudicatory principles.” Astoria
    Fed. Sav. & Loan Ass’n v. Solimino, 
    501 U.S. 104
    , 108
    (1991). A federal statute enacted after a common law doctrine
    has been established will not therefore abrogate the federal
    common law rule unless the statute speaks directly to the
    question addressed by common law. United States v. Texas,
    
    507 U.S. 529
    , 534 (1993). This is because “where a common-
    law principle is well established . . . the courts may take it as
    given that Congress has legislated with an expectation that the
    principle will apply except when a statutory purpose to the
    contrary is evident.” Astoria, 
    501 U.S. at 108
     (internal quota-
    tions and citations omitted) (holding that the court should
    assume Congress drafted the Age Discrimination in Employ-
    ment Act with the common law administrative estoppel doc-
    trine in mind); see also Pasquantino v. United States, 
    544 U.S. 349
    , 359 (2005).
    [2] Whether the PAA preempts the government contractor
    defense is therefore a two-step inquiry. We must first deter-
    mine whether the government contractor defense was well-
    established at the time Congress enacted the operative version
    of the PAA. If so, we must determine whether a statutory pur-
    pose contrary to the government contractor defense is evident.
    The defense fails the first inquiry. Defendants are not enti-
    tled to the government contractor defense, because the statute
    predates clear judicial recognition of any such defense. In
    addition, the statute’s comprehensive liability scheme is
    patently inconsistent with the defense and precludes its opera-
    tion in this case.
    [3] The Supreme Court’s decision in Boyle was filed on
    June 27, 1988. Less than two months later, the PAA was
    amended, on August 20, 1988, to include the pertinent lan-
    IN RE: HANFORD NUCLEAR RESERVATION LITIGATION      9807
    guage establishing exclusive federal jurisdiction for all public
    liability claims arising from nuclear incidents. While the gov-
    ernment contractor defense was technically a recognized com-
    mon law principle at the time Congress enacted the PAA, it
    was hardly a well-established doctrine. See Astoria, 
    501 U.S. at 108
    . (noting that courts should presume Congress legislated
    with an expectation that a common law doctrine would apply
    only if the common-law principle was well-established).
    When drafting the bill, Congress could not have considered
    whether or not the government contractor defense would
    affect liability under the PAA, because the Supreme Court
    defined the defense only a few weeks before the PAA was
    signed into law.
    The origins of the defense in the cases antecedent to Boyle
    do not materially affect this analysis. In 1940, the Supreme
    Court arguably planted the seeds of the government contractor
    defense in Yearsley v. W.A. Ross Constr. Co., 
    309 U.S. 18
    ,
    20-21 (1940). It held that an agent of the government could
    not be held liable under the Takings Clause for the defective
    construction of a dam that damaged land, as long as the agent
    followed government specifications for the dam’s construc-
    tion. The Court limited the applicability of the defense to
    principal-agent relationships where the agent had no discre-
    tion in the design process and completely followed govern-
    ment specifications. Nothing in Yearsley extended immunity
    to military contractors exercising a discretionary governmen-
    tal function. See Boyle, 
    487 U.S. at 524-25
     (J. Brennan, dis-
    senting) (Yearsley is “a slender reed on which to base so
    drastic a departure from precedent” . . . . “[It] has never been
    read to immunize the discretionary acts of those who perform
    service contracts for the Government”).
    While some circuit courts began extending the Yearsley
    doctrine to military contractors as early as the 1960s, see
    McKay v. Rockwell Int’l Corp., 
    704 F.2d 444
    , 448-49 (9th
    Cir. 1983) (citing cases), other circuits held that Yearsley was
    clearly limited to principal-agent relationships and did not
    9808    IN RE: HANFORD NUCLEAR RESERVATION LITIGATION
    apply to military contractors, see, e.g., Bynum v. FMC Corp.,
    
    770 F.2d 556
    , 564 (5th Cir. 1985). In light of the conflicting
    authority on the matter, it is clear that neither the scope nor
    the contours of the defense were well-defined until the
    Supreme Court’s 1988 decision in Boyle. We therefore con-
    clude that the government contractor defense was not well-
    established at the time Congress enacted the PAA.
    Because Congress did not enact the PAA against a back-
    drop of common law principles that included the government
    contractor defense, we cannot grant immunity from liability.
    Astoria, 
    501 U.S. at 108
    . The federal common law defense
    exists only in the absence of explicit statutory directive. Mil-
    waukee v. Illinois, 
    451 U.S. 304
    , 312-13 (1981); Boyle, 
    487 U.S. at 504
    . In this case, Congress drafted a precise, compre-
    hensive litigation scheme for injuries sustained in a nuclear
    incident. The federal courts have recognized this congressio-
    nal intent. O’Conner v. Commonwealth Edison Co., 
    13 F.3d 1090
    , 1099 (7th Cir. 1994); In re TMI Litigation Cases, 
    940 F.2d 832
    , 854-55 (3d Cir. 1991) (“In re TMI Litig.”). That
    scheme governs the conduct of this litigation.
    [4] Congress enacted the PAA with twin goals in mind: to
    provide an incentive to contractors to participate in the
    nuclear industry by limiting their liability, and to compensate
    victims of nuclear accidents. See, e.g., Pub. L. No. 100-408,
    
    102 Stat. 1066
     (1988); S. REP. NO. 100-218, at 4-13 (1987),
    reprinted in 1988 U.S.C.C.A.N. 1476, 1479-88. The Act
    placed Plaintiffs’ state law claims in federal court and pro-
    vided indemnification of Defendants from the federal govern-
    ment for any liability to victims of nuclear incidents. See 
    42 U.S.C. § 2210
    ; S. REP. NO. 100-218, at 13, reprinted in 1988
    U.S.C.C.A.N. at 1484, 1488. To allow those entitled to
    indemnity as government contractors to disclaim any liability
    because they are government contractors would be inconsis-
    tent with the goal of the PAA to provide compensation to vic-
    tims of nuclear incidents. We will not assume that in enacting
    the PAA’s comprehensive scheme, Congress intended, yet
    IN RE: HANFORD NUCLEAR RESERVATION LITIGATION       9809
    failed to state in the Act, that victims of nuclear incidents can-
    not recover tort damages from nuclear operators when the
    operators were pursuing government goals. Accordingly, we
    hold that the government contractor defense is inapplicable as
    a matter of federal law and affirm the district court’s ruling
    on this key issue.
    IV.    Strict Liability.
    Defendants next argue that the district court erred as a mat-
    ter of Washington state law in holding Defendants strictly lia-
    ble for any I-131 emissions from the Hanford facility.
    Defendants challenge that ruling on three grounds: (1) that
    strict liability pursuant to Washington state law may not be
    imposed under the PAA if Defendants released I-131 within
    federally-authorized emission levels; (2) even if state liability
    law applies, the Hanford activity did not meet the “abnor-
    mally dangerous activity” test that warrants strict liability; and
    (3) even if Washington courts would apply a strict liability
    regime, Defendants would be exempted under the “public
    duty” exception that applies generally to heavily regulated
    entities doing potentially hazardous work. For the reasons
    below, we affirm the district court’s imposition of strict liabil-
    ity.
    A.    Federally-Authorized Emissions.
    [5] It is not disputed that the federal government is in
    charge of nuclear safety. “[T]he safety of nuclear technology
    [is] the exclusive business of the Federal Government,” which
    has “occupied the entire field of nuclear safety concerns.”
    Koller v. Pinnacle West Capital Corp., 
    2007 U.S. Dist. LEXIS 9186
     (D. Ariz. Feb. 7, 2007) (second alteration in
    original) (quoting Pac. Gas Elec. Co. v. State Energy Res.
    Conservation & Dev. Comm’n, 
    461 U.S. 190
    , 208, 212
    (1983)). Every federal circuit that has considered the appro-
    priate standard of care under the PAA has concluded that
    nuclear operators are not liable unless they breach federally-
    9810    IN RE: HANFORD NUCLEAR RESERVATION LITIGATION
    imposed dose limits. See, e.g., O’Conner, 
    13 F.3d at 1105
    ; In
    re TMI Litig., 940 F.2d at 859; Roberts v. Fla. Power & Light
    Co., 
    146 F.3d 1305
    , 1308 (11th Cir. 1998); Nieman v. NLO,
    Inc., 
    108 F.3d 1546
    , 1553 (6th Cir. 1997).
    [6] Defendants are thus correct insofar as they point out
    that the clear weight of authority supports the principle that
    federal law preempts states from imposing a more stringent
    standard of care than federal safety standards. Strict liability
    may not be imposed for I-131 releases within federally-
    authorized limits, because any federal authorization would
    preempt state-derived standards of care. To allow a jury to
    decide on the basis of a state’s reasonableness standard of
    care would “put juries in charge of deciding the permissible
    levels of radiation exposure and, more generally, the ade-
    quacy of safety procedures at nuclear plants—issues that have
    explicitly been reserved to the federal government.” In re TMI
    Gen. Publ. Utils. Corp., 
    67 F.3d 1103
    , 1115 (3d Cir. 1995)
    (citing Pacific Gas, 
    461 U.S. at 212
    ). This result would under-
    mine the purpose of a comprehensive and exclusive federal
    scheme for nuclear incident liability.
    Defendants then go further, however, and argue that the
    district court in this case permitted the jury to substitute its
    view of a reasonable emission standard for a government
    standard. The problem with Defendants’ argument is that no
    federal standards governing emission levels existed at the
    time of the I-131 emissions. Defendants try to remedy this
    problem by pointing to “tolerance doses” recommended and
    implemented by military and government scientists working
    on the Hanford project and ask us to equate such recommen-
    dations with federally-authorized emission levels. They are
    not the same.
    These tolerance doses, although established under the aegis
    of the United States Army, did not carry the force of law and
    thus cannot provide the basis for a safe harbor from liability.
    They amounted to no more than site-specific safety rules. The
    IN RE: HANFORD NUCLEAR RESERVATION LITIGATION       9811
    United States Army instructed the Manhattan Engineering
    District to set forth standard, internal operating procedures for
    the plutonium-production process at Hanford. The tolerance
    doses were part of these procedures. The Met Lab scientists
    calculated what they thought were the outer limits of safe
    exposure at the plant. These internal guidelines were, how-
    ever, exactly and only what they claimed to be: internal. They
    were not comprehensive, federal standards governing emis-
    sion levels on which Defendants could rely to relieve them
    from liability for harm they caused.
    Defendants are correct that it would not have been possible
    for an agency to establish emission levels in the early 1940s,
    because the Atomic Energy Act was not enacted until 1954
    and the Nuclear Regulatory Commission was created in 1974.
    In fact, the emissions occurred even prior to the enactment of
    the Administrative Procedure Act in 1946. This history, how-
    ever, undermines Defendants’ position, because it highlights
    the absence of any federal machinery to promulgate legal
    standards on which Defendants could have reasonably relied
    to insulate them from liability to those living and breathing
    twenty-four hours a day in the area surrounding Hanford. The
    need for such standards was not recognized until many years
    later.
    B.   Abnormally Dangerous Activity.
    Defendants next argue that even if state law standards
    apply in this case, the district court erred by holding that
    Washington tort law would impose strict liability. Specifi-
    cally, Defendants contend that operating the Hanford facility
    does not constitute an “abnormally dangerous activity” under
    Washington law. We review de novo the question of whether
    an activity is abnormally dangerous, Langan v. Valicopters,
    Inc., 
    567 P.2d 218
    , 221 (Wash. 1977), and we affirm.
    Washington has adopted the Restatement (Second) of
    Torts, sections 519 and 520, which outline the strict liability
    9812      IN RE: HANFORD NUCLEAR RESERVATION LITIGATION
    regime for abnormally dangerous activities. Klein v. Pyrodyne
    Corp., 
    810 P.2d 917
    , 920 (Wash. 1991); New Meadows Hold-
    ing Co. v. Wash. Water Power Co., 
    687 P.2d 212
    , 215 (Wash.
    1984). Section 519 provides:
    (1) One who carries on an abnormally dangerous
    activity is subject to liability for harm to the person,
    land, or chattels of another resulting from the activ-
    ity, although he has exercised the utmost care to pre-
    vent such harm.
    (2) Such strict liability is limited to the kind of
    harm, the risk of which makes the activity abnor-
    mally dangerous.
    Section 520 lists the factors to be used when determining
    what constitutes an abnormally dangerous activity:
    (a) Whether the activity involves a high degree of
    risk of some harm to the person, land or chattels of
    another;
    (b) Whether the gravity of the harm which may
    result from it is likely to be great;
    (c) Whether the risk cannot be eliminated by the
    exercise of reasonable care;
    (d) Whether the activity is not a matter of common
    usage;
    (e) Whether the activity is inappropriate to the
    place where it is carried on; and
    (f)    The value of the activity to the community.
    RESTATEMENT (SECOND) OF TORTS §§ 519-20 (1977). A court
    does not have to weigh each of the elements listed in § 520
    IN RE: HANFORD NUCLEAR RESERVATION LITIGATION       9813
    equally. Langan, 567 P.2d at 221. One factor, alone, however,
    is generally not sufficient to find an activity abnormally dan-
    gerous. Id.
    [7] Defendants argue that at the time of the emissions in the
    1940s, they did not know the risks that were attributable to
    radioiodine exposure, and therefore § 520’s factors (a)-(c)
    cannot be weighed against them. Any possible injury from
    radiation, however, need not have been actually known by
    Defendants at the time of exposure in order to impose strict
    liability. Under Washington law, if the actual harm fell within
    a general field of danger which should have been anticipated,
    strict liability may be appropriate. Whether an injury should
    have been anticipated does not depend on whether the particu-
    lar harm was actually expected to occur. Koker v. Armstrong
    Cork, Inc., 
    804 P.2d 659
    , 667-68 (Wash. Ct. App. 1991). It is
    sufficient that “the risk created [be] so unusual, either because
    of its magnitude or because of the circumstances surrounding
    it. . . .” Langan, 567 P.2d at 221.
    [8] There is no question that Defendants should have antici-
    pated some of the many risks associated with operating a
    nuclear facility, creating plutonium, and releasing I-131 into
    the atmosphere. It is exactly because of these risks, and the
    potential exposure to liability arising from them, that the gov-
    ernment contracted with Defendants to limit liability in case
    of an accident. For these same reasons, the Met Lab scientists
    recommended dosage limits.
    [9] We agree with the district court that Defendants’ con-
    duct at Hanford was an abnormally dangerous activity under
    the § 520 factors. There was a high degree of risk to people
    and property associated with the Hanford facility and the
    gravity of any harm was likely to be great. See RESTATEMENT
    (SECOND) OF TORTS § 520. Regardless of Defendants’ efforts
    to exercise reasonable care, some I-131 would be released,
    and developing plutonium is hardly an activity of common
    usage. While the value to the community at large, i.e., the
    9814    IN RE: HANFORD NUCLEAR RESERVATION LITIGATION
    nation, of developing an atomic bomb was perceived as high
    and there is pragmatically no very appropriate place to carry
    on such an activity, the § 520 factors on balance support hold-
    ing that Defendants’ activities were abnormally dangerous.
    C.   Public Duty Exception to Strict Liability.
    Defendants’ final defense is that even if their conduct con-
    stituted an abnormally dangerous activity, they are exempted
    from strict liability under Washington law pursuant to the
    “public duty” exception. See RESTATEMENT (SECOND) OF TORTS
    § 521. While this issue presents a close question, we conclude
    that Defendants do not qualify for the exception.
    Section 521 of the Restatement provides:
    The rules as to strict liability for abnormally danger-
    ous activities do not apply if the activity is carried on
    in pursuance of a public duty imposed upon the actor
    as a public officer or employee or as a common car-
    rier.
    Id. As a threshold matter, Washington courts have not yet
    adopted § 521. We must therefore decide what the Washing-
    ton Supreme Court would likely do if confronted with the
    issue. See NLRB v. Calkins, 
    187 F.3d 1080
    , 1089 (9th Cir.
    1999). We hold that the court would likely adopt the public
    duty exception.
    Although they have never explicitly adopted § 521, Wash-
    ington courts have adopted § 519, which governs abnormally
    dangerous activities generally. The comments to § 519 indi-
    cate that the public duty exception is part and parcel of strict
    liability. Comment “a” to § 519 states that “[t]he general rule
    stated in this Section is subject to exceptions and qualifica-
    tions, too numerous to be included within a single section. It
    should therefore be read together with §§ 520 to 524A, by
    which it is limited.” RESTATEMENT (SECOND) OF TORTS, § 519
    IN RE: HANFORD NUCLEAR RESERVATION LITIGATION        9815
    cmt. a. Comment “d” further limits the scope of strict liability
    and states that persons are accountable only for abnormally
    dangerous activities they undertake “for [their] own pur-
    poses.” Id. § 519 cmt. d. A key corollary to this point is that
    strict liability does not apply to activities carried on in pursu-
    ance of a public duty the actor was legally obligated to per-
    form. See id. § 521.
    Although Washington could adopt § 519 without adopting
    the numerous exceptions found in §§ 521-524A, it is unlikely
    that it would do so. Washington adopted wholesale the abnor-
    mally dangerous activity doctrine and its exceptions when
    they existed in the First Restatement. See, e.g., Epperly v.
    Seattle, 
    399 P.2d 591
    , 595 (Wash. 1965); Foster v. Preston
    Mill Co., 
    268 P.2d 645
    , 647 (Wash. 1954). Furthermore, of
    the states that have adopted §§ 519-20, the vast majority has
    also adopted the subsequent exceptions.
    [10] Although widely adopted, the courts that have applied
    the public duty exception have generally done so only to the
    extent a defendant was legally required to perform the
    ultrahazardous activity. See RESTATEMENT (SECOND) OF TORTS,
    § 521, cmt. a. The Washington Supreme Court’s decision in
    Siegler v. Kuhlman, 
    502 P.2d 1181
     (Wash. 1972), supports
    such an application of the public duty doctrine here. The
    defendants in Siegler were a trucking company for Texaco
    and its driver, and the company was not legally obligated as
    a common carrier to carry materials that eventually caused an
    explosive, fatal accident on a highway. The Washington court
    held that the activity was abnormally dangerous and that the
    defendants could be held strictly liable for the accident. It is
    therefore most likely that the Washington Supreme Court
    would apply strict liability when the defendant was perform-
    ing a dangerous activity for “his own purpose,” and would
    apply the public duty exception only in the appropriate case
    when the defendant was engaged in a legally-obligated activ-
    ity, such as a regulated common carrier bound to carry haz-
    ardous substances.
    9816    IN RE: HANFORD NUCLEAR RESERVATION LITIGATION
    Defendants argue that in light of the exceptional and patri-
    otic circumstances under which they operated Hanford, we
    should treat them as analogous to public employees who
    would qualify for the exception. Although Defendants are
    correct that we generally do not parse the language of a
    restatement as meticulously as that of a statute, and we will
    apply it “when the purposes it seeks to serve dictate its appli-
    cation,” McKay, 
    704 F.2d at 447
    , Defendants do not satisfy
    the exception’s purpose in this case. Defendants are not public
    officers or employees or common carriers, see RESTATEMENT
    (SECOND) OF TORTS § 521, and they were not legally obligated
    to operate Hanford.
    The prototypical example of a defendant entitled to the
    public duty exception is a utility company that is legally
    required to transport an ultrahazardous good, such as electric-
    ity, and causes injury to someone during transport. Courts
    have recognized a public duty exception in such cases,
    because common carriers must accept, carry, and deliver all
    goods offered to them for transport within the scope of the
    operating authority set forth in their permits. See, e.g., 
    16 U.S.C. § 824
     et. seq. (granting the Federal Energy Regulatory
    Commission authority to establish guidelines for common
    carriers of electricity in interstate commerce); United States v.
    W. Processing Co., 
    756 F. Supp. 1416
    , 1421 (W.D. Wash.
    1991). They cannot discriminate against customers or refuse
    to accept commodities that may be dangerous for transport.
    
    Id.
    [11] The case law therefore illustrates that the duty
    involved is the legal obligation to perform the abnormally
    dangerous activity in accordance with government orders.
    See, e.g., EAC Timberlane v. Pisces, Ltd., 
    745 F.2d 715
    , 721
    n.12 (1st Cir. 1984) (noting that the public duty must be one
    imposed on the actor) (citing Actiesselskabet Ingrid v. Central
    R.R. Co. of New Jersey, 
    216 F. 72
     (2d Cir. 1914); Town of
    East Troy v. Soo Line R.R. Co., 
    409 F. Supp. 326
    , 329 (E.D.
    Wis. 1976) (no strict liability for spillage of carbolic acid by
    IN RE: HANFORD NUCLEAR RESERVATION LITIGATION       9817
    derailment of common carrier train); Christ Church Parish v.
    Cadet Chem. Corp., 
    199 A.2d 707
    , 708-09 (Conn. Super. Ct.
    1964) (transportation of twenty tons of various chemical sub-
    stances); Pecan Shoppe of Springfield v. Tri-State Motor
    Transit Co., 
    573 S.W.2d 431
    , 438-39 (Mo. Ct. App. 1978)
    (transporter of explosives); Pope v. Edward M. Rude Carrier
    Corp., 
    75 S.E.2d 584
    , 595-96 (W. Va. 1953) (transporter of
    explosives). Qualifying entities must be operating pursuant to
    the mandate and control of the government; they must have
    little discretion over the manner in which they conduct their
    activities. See Actiesselskabet Ingrid, 216 F. at 78 (“It cer-
    tainly would be an extraordinary doctrine for courts . . . to say
    that a common carrier is under legal obligation to transport
    dynamite and is an insurer against any damage which may
    result in the course of transportation, even though it has been
    guilty of no negligence which occasioned the explosion which
    caused the injury.”); Pope, 
    75 S.E. 2d at 591-92
     (holding no
    strict liability for common carrier transport of explosives); but
    see Lamb v. Martin Marietta Energy Sys., Inc., 
    835 F. Supp. 959
     (W.D. Ky. 1993) (applying the public duty exception to
    a nuclear facility because under Kentucky law the public duty
    exception includes entities engaged in activities of public
    necessity even when there is no legal duty to perform them).
    [12] There was no government mandate here. The events
    giving rise to this litigation occurred before the government
    developed rules or the ability to control nuclear facilities. The
    government was relying on the expertise of defendants and
    not vice versa.
    [13] We should not confuse the legal concept of a public
    duty with popular notions of patriotic duty taken at personal
    sacrifice. Defendants may well have been acting at the gov-
    ernment’s urging during wartime. The public duty exception,
    however, was developed under state law in recognition of the
    need to protect private actors who are legally required to
    engage in ultrahazardous activities. No matter how strongly
    Defendants may have felt a patriotic duty, they had no legal
    9818         IN RE: HANFORD NUCLEAR RESERVATION LITIGATION
    duty to operate Hanford, and they are, therefore, not entitled
    to the public duty exception. The district court correctly found
    defendants subject to strict liability.
    V.        Statute of Limitations.
    A.     Waiver.
    Defendants argue for the first time on appeal that Bell-
    wether Plaintiff Gloria Wise’s lawsuit was untimely, because
    pursuant to Am. Pipe & Constr. Co. v. Utah, 
    414 U.S. 538
    (1974), Wise lost the benefit of any statute of limitations toll-
    ing when she filed a separate, individual suit prior to the
    denial of class certification. Defendants arguably have waived
    this claim, because they did not raise the issue below suffi-
    ciently for the district court to rule on the matter. McMillan
    v. United States, 
    112 F.3d 1040
    , 1047 (9th Cir. 1997); In re
    E.R. Fegert, Inc., 
    887 F.2d 955
    , 957 (9th Cir. 1989). We have
    discretion, however, to overlook any waiver. See United
    States v. Bynum, 
    327 F.3d 986
    , 990 (9th Cir. 2003). We exer-
    cise such discretion in this case, because the issue of whether
    Wise’s lawsuit was tolled pending class certification is a
    purely legal question, see id.; both parties concede that the
    issue is “important,” and addressing the issue is consistent
    with the purpose of a bellwether trial in clarifying and stream-
    lining the relevant issues. The issue should therefore be set-
    tled now.
    We recognize that the results of the Hanford bellwether
    trial are not binding on the remaining plaintiffs. See, e.g., In
    re Hanford Nuclear Res. Litig., No. 91-03015, Dkt. #1294 at
    164-65 (E.D. Wash. June 3, 2003). Nevertheless, according to
    counsel for the parties, the purpose of the bellwether trial was
    to “establish the relative strengths and weaknesses of the par-
    ties, spread out mainly for settlement purposes. . . .” Id. at
    155, 165. The bellwether trial was meant to be a “learning
    process.” Id. at 161. The parties also state in their briefs that
    there are “numerous” other plaintiffs who face a similar stat-
    IN RE: HANFORD NUCLEAR RESERVATION LITIGATION        9819
    ute of limitations hurdle. It would defeat the purpose of a bell-
    wether trial and only deter settlement longer to refrain from
    deciding this purely legal issue at the earliest possible stage.
    Our resolution will save any potentially time-barred plaintiffs
    from expending additional resources and energy on futile
    legal proceedings.
    B.   Application of American Pipe.
    In April 1994, the Hanford plaintiffs moved for class certi-
    fication. The district court reserved ruling on certification
    under the opt-out provision of Federal Rule of Civil Proce-
    dure 23(b)(3). Plaintiffs eventually withdrew their request for
    certification, but not until May 2003, after the first series of
    appeals was decided by this circuit. Accordingly, the district
    court held that the statute of limitations was tolled for all
    putative class members from April 1994 until May 2003.
    Plaintiff Wise was diagnosed with thyroid cancer in April
    1993, three years after the first class action complaints were
    filed and one year before Plaintiffs moved for class certifica-
    tion. Wise filed an individual suit in district court in July
    1997. If the date of diagnosis is the triggering date for the
    statute of limitations, her individual suit was apparently
    untimely, because Washington’s statute of limitations for per-
    sonal injury claims is three years. Wise’s suit would have
    been timely only if she was entitled to the tolling that began
    for the class action plaintiffs on April 15, 1994. Defendants
    now contend that Wise forfeited these tolling benefits when
    she filed her individual suit prior to the district court granting
    or denying class certification. Wise contends she is entitled to
    tolling as a member of the class pursuant to American Pipe.
    [14] In American Pipe, 
    414 U.S. at 554
    , the Supreme Court
    held that the commencement of a class action suspends the
    applicable statute of limitations as to all asserted members of
    the class who would have been parties had the suit been per-
    mitted to continue as a class action. 
    Id.
     The tolling period
    9820    IN RE: HANFORD NUCLEAR RESERVATION LITIGATION
    ends, and the statute runs anew, once class certification is
    granted or denied. Tosti v. City of Los Angeles, 
    754 F.2d 1485
    , 1488 (9th Cir. 1985). The issue in this case, which is
    one of first impression in our circuit, is whether American
    Pipe also permits tolling for a plaintiff who files a separate
    action pending class certification. The overwhelming weight
    of authority answers the question in the negative.
    The Sixth Circuit, which is the only circuit to have
    addressed the issue directly, has also said no. It held that the
    purposes of class action tolling under American Pipe “are not
    furthered when plaintiffs file independent actions before deci-
    sion on the issue of class certification.” Wyser-Pratte Mgmt.
    Co., Inc. v. Telxon, 
    413 F.3d 553
    , 569 (6th Cir. 2005). Such
    purposes are only furthered “when plaintiffs delay until the
    certification issue has been decided.” 
    Id.
     The Second Circuit
    tangentially reached a similar conclusion two decades earlier,
    when it stated that “[t]he policies behind Rule 23 and Ameri-
    can Pipe would not be served, and in fact would be disserved,
    by guaranteeing a separate suit at the same time that a class
    action is ongoing.” Glater v. Eli Lilly & Co., 
    712 F.2d 735
    ,
    739 (1st Cir. 1983). Countless federal district courts have
    come to the similar conclusion that “[a]pplying the tolling
    doctrine to separate actions filed prior to class certification
    would create the very inefficiency that American Pipe sought
    to prevent.” In re Worldcom, Inc. Sec. Litig., 
    294 F. Supp. 2d 431
    , 451 (S.D.N.Y. 2003) (citing cases); see also In re Heri-
    tage Bond Litig., 
    289 F. Supp. 2d 1132
    , 1150 (C.D. Cal.
    2003).
    [15] We share the prevailing view that precluding tolling in
    this situation satisfies the judicial economy concerns of Amer-
    ican Pipe without jeopardizing protections that exist for plain-
    tiffs who opt out of the class. We should not allow a plaintiff
    to file an individual suit, which is in essence a signal that the
    plaintiff is opting out of a class, and then simultaneously give
    the same plaintiff class action benefits. “The parties and
    courts [should] not be burdened by separate lawsuits which
    IN RE: HANFORD NUCLEAR RESERVATION LITIGATION       9821
    . . . may evaporate once a class has been certified.” Wyser-
    Pratte, 
    413 F.3d at 569
     (quoting In re Worldcom, 
    294 F. Supp. 2d at 452
    ). Courts have recognized that class action
    tolling is intended to avoid the injustice of requiring putative
    class members to file individual suits or to lose their claims,
    but the benefits should not be abused. Tolling is not “intended
    to be a tool to manipulate limitations periods for parties who,
    intending all along to pursue individual claims, assert reliance
    on the proposed class action just long enough to validate their
    otherwise time barred claims.” Rahr v. Grant Thornton, LLP,
    
    142 F. Supp. 2d 793
    , 800 (N.D. Tex. 2000). Accordingly, we
    hold that this individual who filed a separate suit pending a
    decision on class certification loses the benefit of any statute
    of limitations tolling under American Pipe.
    [16] On the record before us, we are unable to determine
    whether Plaintiff Wise’s individual suit was timely absent
    American Pipe tolling, because we do not know the triggering
    date under Washington law for the statute of limitations in her
    case. We therefore remand to the district court for further pro-
    ceedings on this issue consistent with our opinion.
    VI.   Medical Monitoring Claims.
    Plaintiffs Pamela Durfey, Paulene Echo Hawk, and Doro-
    thy George’s only claim on appeal is for medical monitoring.
    They do not yet have any diseases attributable to Hanford
    radiation. Because in all relevant respects Plaintiffs are analo-
    gous to the plaintiffs who requested medical monitoring in
    2002 in Berg, 
    293 F.3d 1127
    , Plaintiffs’ claims were origi-
    nally stayed pending this court’s decision in that case.
    We then decided Berg, in which we held that claims for
    medical monitoring are not compensable under the PAA,
    because they do not constitute claims of “bodily injury, sick-
    ness, disease, or death . . .” Berg, 
    293 F.3d at
    1132-33 (citing
    
    42 U.S.C. § 2014
    (q)). After our decision, Plaintiffs in this
    case asked the district court to remand their medical monitor-
    9822    IN RE: HANFORD NUCLEAR RESERVATION LITIGATION
    ing claims to state court. They claimed that Berg abrogated
    subject matter jurisdiction in federal court for all medical
    monitoring claims. Defendants opposed remand, arguing that
    Berg did not remove the district court’s subject matter juris-
    diction, but held only that a medical monitoring claim was not
    cognizable under the PAA.
    [17] Although in Berg we referred to bodily injury as a
    jurisdictional prerequisite, 
    id. at 1131-33
    , we used the term
    “jurisdictional” in the loose sense, perhaps too loose, to mean
    that medical monitoring claims were not compensable under
    the PAA. We have been guilty of such expansive use of the
    term before. See Khalsa v. Weinberger, 
    779 F.2d 1393
    , 1396
    n.2 (9th Cir. 1985) (“. . . jurisdiction has many possible mean-
    ings, ranging from subject matter jurisdiction to the power to
    grant the relief requested . . . ”). The district court in this case
    clearly had subject matter jurisdiction under the PAA to
    decide the issue; the district court simply did not have the
    power to grant the relief requested. See 
    id.
    [18] The PAA is the exclusive means of compensating vic-
    tims for any and all claims arising out of nuclear incidents.
    Berg, 
    293 F.3d at 1132
    ; In re TMI Litig., 940 F.2d at 854; see
    also 
    42 U.S.C. § 2014
    (hh), (w) (federal courts have jurisdic-
    tion over public liability actions, defined as “any suit asserting
    . . . any legal liability arising out of or resulting from a nuclear
    accident”) (emphasis added). This result is consistent with
    Congress’s explicit intent in enacting the 1988 Amendments
    and avoiding piecemeal litigation arising from nuclear inci-
    dents. We therefore affirm the district court’s exercise of
    jurisdiction over Plaintiffs’ medical monitoring claims and its
    conclusion pursuant to our decision in Berg that they were not
    compensable under the Act. The district court properly denied
    Plaintiffs’ request for a remand to state court.
    VII.   First Bellwether Trial.
    The remaining issues on appeal stem from a variety of legal
    and evidentiary rulings in the two trials. Three of the six Bell-
    IN RE: HANFORD NUCLEAR RESERVATION LITIGATION        9823
    wether Plaintiffs, Goldbloom, Buckner, and Carlisle, lost at
    the first trial. Three of their evidentiary challenges constitute
    reversible error; the remaining arguments are meritless.
    A.   Causation.
    We first decide whether under Washington law the district
    court properly instructed the jury in the bellwether trial on
    “but-for,” and not “substantial factor,” causation. Plaintiffs
    contend that the more lenient substantial factor test should
    apply because other factors could have contributed to their ill-
    nesses, such as smoking and genetics. We review the district
    court’s application of Washington law de novo, Ostad v. Or.
    Health Scis. Univ., 
    327 F.3d 876
    , 883 (9th Cir. 2003), and we
    affirm the district court’s instruction on but-for causation.
    Under the PAA, Washington state law controls the standard
    of causation to be used in this case. See 
    42 U.S.C. § 2014
    (hh).
    (“A public liability action shall be deemed to be an action
    arising under section 170 [
    42 U.S.C. § 2210
    ], and the substan-
    tive rules for decision in such action shall be derived from the
    law of the State in which the nuclear incident involved occurs,
    unless such law is inconsistent with the provisions of such
    section.”). Washington courts will depart from the standard
    but-for causation instruction in favor of the substantial factor
    test only in three rare circumstances: (1) the plaintiff was
    excusably ignorant of the identity of the tortfeasor who
    caused his injury; (2) the plaintiff probably would have been
    injured anyway, but lost a significant chance of avoiding the
    injury; or (3) the plaintiff has been injured by multiple inde-
    pendent causes, each of which would have been sufficient to
    cause the injury. Gausvik v. Abbey, 
    107 P.3d 98
    , 108 (Wash.
    Ct. App. 2005); see also Daugert v. Pappas, 
    704 P.2d 600
    ,
    605-06 (Wash. 1985).
    The parties agree that the first and second exceptions are
    not at issue here. Plaintiffs know the identity of the tortfeasors
    and had no chance to avoid injury. See, e.g., Lockwood v.
    9824         IN RE: HANFORD NUCLEAR RESERVATION LITIGATION
    AC&S, Inc., 
    744 P.2d 605
    , 613 (Wash. 1987) (applying the
    substantial factor test when there is no doubt that asbestos was
    the cause of a plaintiff’s asbestosis, but the plaintiff cannot
    identify which manufacturer is responsible); Mavroudis v.
    Pittsburgh-Corning Corp., 
    935 P.2d 684
    , 687 (Wash. Ct.
    App. 1997).
    [19] Plaintiffs therefore appear to rely on the third type of
    substantial factor causation, which applies when there have
    been “multiple, independent causes,” each of which alone is
    sufficient to cause the injury. Gausvik, 
    107 P.3d at 108
    . There
    are two requirements they must satisfy (1) there must have
    been multiple causes of the injury; and (2) any one cause
    alone was sufficient to cause the injury. 
    Id.
     Plaintiffs can not
    satisfy the second requirement. Plaintiffs instead ask us to
    expand the substantial factor doctrine and apply the test when
    there are potentially multiple causes of each plaintiff’s injury,
    such as radiation, smoking, genetics, or pregnancy, even
    though Plaintiffs cannot show that Hanford radiation alone
    would have been sufficient to cause the injury. Their reading
    of Washington law would allow the substantial factor test to
    supplant but-for causation in virtually all toxic tort cases.
    Such a result is inconsistent with existing Washington law,
    which applies the substantial factor test in very limited cir-
    cumstances. See also RESTATEMENT (THIRD) OF TORTS § 26
    cmt. j (Proposed Final Draft 2005) (eliminating the substantial
    factor test). We therefore hold that the district court properly
    instructed the jury on but-for causation.
    B.        Evidentiary Rulings Constituting Reversible Error.
    i.    Cross-Examination of Dr. Davies.
    Plaintiffs raise two issues with respect to Defendants’
    cross-examination of Plaintiffs’ endocrinologist expert Dr.
    Terry Davies, in the first bellwether trial. The first issue con-
    cerns the district court’s ruling that Dr. Davies could not tes-
    tify that he authored articles on I-131’s effect on thyroid cells.
    IN RE: HANFORD NUCLEAR RESERVATION LITIGATION        9825
    The second issue is Defendants’ cross-examination of Dr.
    Davies with deposition testimony of a non-testifying expert.
    These errors surrounding Dr. Davies’ testimony, taken
    together, were prejudicial to Plaintiffs’ case. We therefore
    must remand for a new trial.
    With respect to Dr. Davies’ pre-litigation scholarship, the
    district court barred Plaintiffs from asking him whether he has
    “published any peer reviewed articles or papers regarding the
    capacity of I-131 to kill or damage thyroid cells.” The record
    reveals that the district court believed Dr. Davies could not
    testify about any pre-litigation articles on this subject, because
    Dr. Davies had not written any peer-reviewed scientific article
    concluding that doses at less than 100 rads can cause autoim-
    mune disease.
    This ruling was an abuse of discretion, because it deprived
    the jury of testimony from Dr. Davies about the extent of his
    pre-litigation expertise regarding causes of thyroid illness.
    That Dr. Davies had not written any articles specifically
    directed to causation below 100 rads does not mean Dr.
    Davies’ work on causation generally was inadmissible. Plain-
    tiffs’ key witness on causation extensively researched and
    authored scholarship on the capacity of I-131 emissions to kill
    thyroid cells, and the jury was entitled to know the reach of
    his expertise.
    Standing alone, this error might not be prejudicial; there is,
    however, a more serious problem with the presentation of Dr.
    Davies’ testimony. Defendants were allowed to impeach one
    of Plaintiffs’ key expert witnesses with inadmissible evidence,
    hearsay statements that Defendants themselves successfully
    excluded from Plaintiffs’ case-in-chief.
    Prior to trial, Plaintiffs proffered the deposition testimony
    of epidemiologist Dr. A. James Ruttenber. According to
    Plaintiffs, Dr. Ruttenber would have testified that although
    current epidemiological studies prove only that radiation
    9826    IN RE: HANFORD NUCLEAR RESERVATION LITIGATION
    above 40 rads can cause thyroid disease, those studies do not
    preclude causation at lower dosages. On Defendants’ motion,
    the district court excluded this testimony, finding it was too
    speculative. Having learned that the most probative part of
    Dr. Ruttenber’s testimony was no longer admissible, Plaintiffs
    chose not to call him to the stand.
    Plaintiffs, instead, called Dr. Davies to testify that low dos-
    ages of radiation could cause thyroid disease. Dr. Davies had
    relied on some of Dr. Ruttenber’s dosage estimates in prepar-
    ing his pretrial expert report, but he never read nor relied on
    Dr. Ruttenber’s deposition in rendering his expert opinion.
    Even though Dr. Ruttenber’s causation testimony has been
    ruled inadmissible prior to trial, defense counsel on cross-
    examination used Dr. Ruttenber’s deposition to impeach Dr.
    Davies’ testimony. Among many other questions, defense
    counsel asked the following regarding Dr. Ruttenber’s deposi-
    tion:
    Q: And doctor, are you aware that Doctor Rutten-
    ber has said that the epidemiological literature can
    only show an increased risk of autoimmune thyroidi-
    tis down to 40 rads? . . . .
    Q: Did Doctor Ruttenber ever identify to you any
    epidemiological studies that reported that doses at 10
    rad increased the risk of autoimmune thyroid dis-
    ease? . . .
    Q: Yeah, and page 75 at the bottom, lines 23 to 25,
    “Doctor Ruttenber, is it your testimony that the epi-
    demiology gets you down to increased risk of
    autoimmune thyroiditis at point 4 gray?” . . . [ ] now,
    were you aware that Doctor Ruttenber had taken that
    position?”
    Plaintiffs made continuing objections to this cross-
    examination, but the district court permitted the questions.
    IN RE: HANFORD NUCLEAR RESERVATION LITIGATION       9827
    Dr. Ruttenber’s statements should not have been used to
    impeach Dr. Davies because they were inadmissible hearsay
    on which Dr. Davies did not rely. We agree with the Fifth Cir-
    cuit that reports of other experts cannot be admitted even as
    impeachment evidence unless the testifying expert based his
    opinion on the hearsay in the examined report or testified
    directly from the report. Bryan v. John Bean, 
    566 F.2d 541
    ,
    546-47 (5th Cir. 1978) (citing Box v. Swindle, 
    306 F.2d 882
    (5th Cir. 1962)); see also United States v. Layton, 
    549 F. Supp. 903
    , 920-21 (N.D. Cal. 1982). Because Dr. Davies did
    not rely on Dr. Ruttenber’s deposition, and because the trial
    court had excluded the deposition testimony as inadmissible
    hearsay, Defendants should not have been allowed to use the
    testimony to impeach Dr. Davies’ credibility.
    Defendants urge us to find that the error is harmless.
    Defendants, however, overlook their own emphasis on the
    significance of Dr. Davies’ testimony and his credibility to the
    jury. Defendants read a large portion of Dr. Davies’ cross-
    examination back to the jury in closing arguments, highlight-
    ing how Dr. Ruttenber’s deposition testimony rendered Dr.
    Davies’ testimony not credible. They then stated:
    [I]f you have Ruttenber saying 40 rads as of today,
    based on his review of radiation epidemiology, how
    does Davies get away with saying at 10 rads their
    dose; we say it’s closer to 6. How does Davies get
    away with offering an opinion on causation? It’s just
    not credible.
    [20] Dr. Davies was the key witness on causation and
    Defendants’ strategy was to cast doubt on his opinion. They
    did just that by improperly using Dr. Ruttenber’s deposition.
    The prejudice to Plaintiffs was exacerbated by the court’s rul-
    ing that Plaintiffs were unable to rehabilitate Dr. Davies’
    credibility with evidence of his pre-litigation, peer-reviewed
    articles on causation. Dr. Davies’ endocrinologist testimony
    on causation was particularly probative, because Plaintiffs
    9828      IN RE: HANFORD NUCLEAR RESERVATION LITIGATION
    already had lost the key expert’s epidemiological testimony,
    Dr. Ruttenber’s opinion, regarding causation. We thus have
    no choice but to reverse the verdicts against Plaintiffs Gold-
    bloom, Carlisle, and Buckner and remand for a new trial.
    ii.   Hurthle Cell Evidence.
    There is an additional ground for reversal with    respect to
    Plaintiff Goldbloom. The district court erred          when it
    instructed the jury to disregard Dr. Peters’ expert   testimony
    that Goldbloom’s thyroid contained Hurthle cells,     which are
    indicative of some kind of injury to the thyroid.
    Although Dr. Peters’ pretrial expert report contained no
    evidence regarding the presence of Hurthle cells in Gold-
    bloom’s thyroid, defense counsel did not object to the testi-
    mony at trial. Partway through deliberations, the jury astutely
    asked whether it could consider Dr. Peters’ testimony even
    though evidence regarding Hurthle cells was not in the expert
    report. The district court held a conference with the parties to
    discuss the jury’s question. Plaintiffs argued that the jury
    should be able to consider the Hurthle cell evidence, because
    Defendants did not object to its admission at trial. Defendants
    argued that the court should instruct the jury to disregard the
    evidence, because it was not contained in Dr. Peters’ pretrial
    report. The district court agreed with Defendants and
    instructed the jury to disregard the Hurthle cell testimony.
    This ruling was erroneous. It is a rare circumstance when
    the court may exclude evidence after the close of the parties’
    cases. Jerden v. Amstutz, 
    430 F.3d 1231
    , 1236-37 (9th Cir.
    2005), amended on other grounds, 
    2006 U.S. App. LEXIS 673
     (9th Cir. Jan. 12, 2006). The reasons for such caution are
    clear. If the parties have already rested, they no longer have
    a chance to provide a curative response to the excluded evi-
    dence. 
    Id. at 1237
    . They also do not have a chance to present
    the testimony in another fashion, such as calling an additional
    witness. 
    Id.
     (citing Bartleson v. United States, 
    96 F.3d 1270
    ,
    IN RE: HANFORD NUCLEAR RESERVATION LITIGATION        9829
    1278 (9th Cir. 1996)). And most pertinent to this case, it is
    impossible to erase from the jury’s minds any arguments that
    were made during closing summation about the belatedly-
    excluded evidence.
    In this case, not only did Defendants fail to object to the
    Hurthle cell evidence, they used the evidence themselves,
    pointing to the testimony during closing summation as evi-
    dence that Dr. Peters was not a reliable witness. Defendants
    should not have been allowed to reap the benefit of a tardy
    exclusion of Plaintiff’s evidence after they used the same evi-
    dence in their closing argument as a basis for impeachment.
    [21] The error in excluding the evidence was prejudicial.
    Plaintiff Goldbloom did not have an opportunity to remedy
    the error, because the evidence was not excluded until after
    the parties had rested. Her only remedy was to seek a mistrial.
    The error in excluding the Hurthle cell evidence, when cou-
    pled with the errors above, thus warrants a new trial.
    C.     Remaining Evidentiary Challenges.
    Plaintiffs’ remaining claims are all challenges to various
    evidentiary rulings. To help facilitate the bellwether process,
    we briefly address each, although none has merit.
    i.    Dr. Ruttenber’s Testimony.
    [22] The district court did not err in prohibiting Plaintiffs’
    epidemiologist expert, Dr. Ruttenber, from testifying that sci-
    entific extrapolation supports a finding that radiation below
    40 rads could cause hypothyroidism or autoimmune thyroidi-
    tis. Plaintiffs assert that the district court’s rulings impermiss-
    ibly required epidemiological studies to be a prerequisite to
    causation testimony. See In re Hanford, 
    292 F.3d 1124
    ; Ken-
    nedy v. Collagen Corp., 
    161 F.3d 1226
    , 1229-30 (9th Cir.
    1998). The court’s ruling, however, did not go that far. The
    court only precluded Dr. Ruttenber from, first, speculating
    9830       IN RE: HANFORD NUCLEAR RESERVATION LITIGATION
    that such extrapolation would likely produce results showing
    causation below 40 rads, and, second, stating that current epi-
    demiological data do not contradict or prevent such a finding.
    Because the data Dr. Ruttenber used to make these two con-
    clusions were not reliable, see Daubert v. Merrell Dow
    Pharms., 
    509 U.S. 579
    , 589 (1993), the district court did not
    abuse its discretion in excluding Dr. Ruttenber’s opinion.
    ii.    Alternative Causes of Thyroid Disease.
    [23] The district court also did not err in permitting Defen-
    dants to cross-examine Plaintiffs’ experts on alternative
    causes of thyroid disease. Plaintiffs’ chosen methodology for
    proving causation was differential diagnosis, which is a pro-
    cess by which an expert compiles a comprehensive list of
    potential causes and then engages in a process of elimination
    to reach the most likely cause. See Clausen v. M/W New Car-
    issa, 
    339 F.3d 1049
    , 1057-58 (9th Cir. 2003). Plaintiffs’
    experts enumerated possible causes of Plaintiffs’ diseases,
    such as genetic predisposition, pregnancy, and stress, and then
    eliminated them, leaving radioiodine as the only probable
    cause. Having put these alternative causes at issue, Plaintiffs
    could not expect Defendants not to question the experts’
    rejection of them. Defendants were entitled to impeach the
    experts’ methodology and their underlying conclusions.
    iii.    Indemnification.
    [24] Plaintiffs challenge the district court’s ruling that
    Plaintiffs could not tell the jury that the federal government
    would indemnify Defendants for any liability imposed. Evi-
    dence of indemnification is generally inadmissible but may be
    used to show prejudice or bias of a witness. See, e.g., FED. R.
    EVID. 411. The only evidence to which a question of govern-
    ment bias might have arisen, however, was the Hanford Envi-
    ronment Dose Reconstruction Project (“HEDR”) and
    Plaintiffs stipulated to the accuracy of this document prior to
    trial. That stipulation is binding. U.S. Dep’t of Labor v. Kerr-
    IN RE: HANFORD NUCLEAR RESERVATION LITIGATION    9831
    McGee Chem. Corp., 
    15 OSHC (BNA) 2070
     (9th Cir. 1993);
    Am. Title Ins. Co. v. Lacelaw Corp., 
    861 F.2d 224
    , 226 (9th
    Cir. 1988). There was thus no permissible ground on which
    Plaintiffs could introduce evidence of indemnification. The
    district court did not err in its application of Rule 411.
    iv.     Dr. Hill’s Testimony.
    [25] Plaintiffs’ final contention on appeal is that the district
    court abused its discretion when it prohibited Plaintiffs’
    expert Dr. Hill from comparing radioiodine causation in ani-
    mals to causation in humans. This ruling was not an abuse of
    discretion, because the information was not contained in Dr.
    Hill’s pretrial expert report and Defendants were not allowed
    to question Dr. Hill regarding animal studies and thyroid dis-
    ease at his deposition.
    VIII.        Rhodes’ Second Trial.
    Plaintiff-Appellant Shannon Rhodes suffers from several
    thyroid problems, the most serious of which is thyroid cancer.
    Pursuant to the stipulation prior to trial, Rhodes was exposed
    to Hanford radiation of 2.3 to 17 rads. At the bellwether trial,
    she offered the testimony of her expert witness, Dr. Inder
    Chopra, who testified that it was more probable than not that
    Hanford radiation caused Rhodes’ cancer. The jury failed to
    reach a decision on Rhodes’ claims, however, and the trial
    court was forced to order a mistrial. In November 2005,
    Rhodes tried her case for a second time, and the second jury
    rendered a verdict for Defendants. Rhodes’ appeals several
    legal and evidentiary rulings from her second trial.
    A.     Juror Misconduct.
    [26] Rhodes claims that the district court erred in denying
    her post-trial motion for a new trial, because the jury improp-
    erly considered extrinsic evidence during its deliberations.
    Rhodes proffers the signed affidavit of a juror stating that
    9832    IN RE: HANFORD NUCLEAR RESERVATION LITIGATION
    “during deliberations and immediately after the first of several
    votes were taken on the issue of causation, one of the jurors
    announced that this was Mrs. Rhodes second trial on the very
    issues that we were to decide and that she had lost in the first
    trial.”
    A party is entitled to a new trial when the jury obtains or
    uses evidence that has not been introduced during trial only
    if the improperly considered evidence was extrinsic. United
    States v. Keating, 
    147 F.3d 895
    , 900 (9th Cir. 1998). The dis-
    trict court looked at the trial record as a whole and decided
    that any evidence regarding Rhodes’ previous trial came from
    accidental, off-hand comments during the second trial, and
    thus the evidence was not extrinsic.
    We have conducted an independent review of the record,
    United States v. Madrid, 
    842 F.2d 1090
    , 1092 (9th Cir. 1988),
    and we affirm. There were several instances during Rhodes’
    trial when the first litigation was mistakenly mentioned by
    either a witness or an attorney and from which the jurors
    could have inferred that Rhodes had litigated these same
    claims before and “lost.” We agree with the district court that
    because the evidence was not extrinsic, there was no juror
    misconduct.
    B.   Voir Dire.
    [27] The district court did not err in refusing to hold an evi-
    dentiary hearing regarding possible juror misconduct during
    voir dire. A motion for a new trial based on juror dishonesty
    during voir dire requires a showing that (1) a juror failed to
    answer honestly a material question; and (2) a correct answer
    would have provided a valid basis for a challenge for cause.
    Price v. Kramer, 
    200 F.3d 1237
    , 1254 (9th Cir. 2000). Other
    than the affidavit, which stated that a juror admitted during
    deliberations that he read about Rhodes’ prior trial, Rhodes
    does not proffer any evidence that the juror lied during voir
    dire. The juror who read about Rhodes’ trial easily could have
    IN RE: HANFORD NUCLEAR RESERVATION LITIGATION         9833
    done so after the trial began. He also could have read about
    it in the medical report that was admitted as evidence, in
    which Rhodes’ own doctor at the time of the first bellwether
    trial noted that Rhodes was stressed because her litigation was
    not going well. Rhodes has not established any juror miscon-
    duct entitling her to a new trial.
    C.   Reference to Impeachment Evidence as “Totally
    Collateral.”
    During trial, the district court referred to evidence pres-
    ented by Rhodes to impeach a defense expert as “totally col-
    lateral.” The district court later went on the record and
    admitted his comment was a mistake. Rhodes contends that
    the district court’s comment unfairly prejudiced the jury in
    favor of the defense, entitling her to a new trial. There was no
    undue prejudice.
    [28] We review a judge’s comments during trial for an
    abuse of discretion and reverse only if they “projected to the
    jury an appearance of advocacy or partiality.” United States
    v. Parker, 
    241 F.3d 1114
    , 1119 (9th Cir. 2001). A trial court
    has substantial leeway in overseeing the presentation of evi-
    dence, because it is most familiar with the dynamics of a pro-
    ceeding and the dangers of jury confusion. See, e.g., S.M. v.
    J.K., 
    262 F.3d 914
    , 919 (9th Cir. 2001). The district court’s
    reference to certain Plaintiff’s testimony as “totally collateral”
    when sustaining Defendants’ objection, although an admitted
    mistake, did not project an appearance of advocacy or partial-
    ity that warrants reversal in this case.
    D.   “Best Estimate” Requirement.
    Plaintiff next contends that the district court erred in requir-
    ing Dr. Hoffman to give a “best estimate” of the dose of radi-
    ation received by Rhodes. At the bellwether trial, Dr.
    Hoffman testified to a range of possible dosages for each indi-
    vidual with a certain percentage of confidence (i.e. a confi-
    9834    IN RE: HANFORD NUCLEAR RESERVATION LITIGATION
    dence interval). Defendants objected to this use of confidence
    intervals in Rhodes’ second trial, claiming they would mis-
    lead the jury and encourage them mistakenly to believe that
    there was a high likelihood that Rhodes was exposed to radia-
    tion near the upper-boundary of the dosage range, when in
    fact, the expert was only capable of endorsing the entire range
    with ninety-percent confidence. Plaintiff agreed to the district
    court’s suggestion that Dr. Hoffman testify to a range of pos-
    sible dosage exposure, but also give a “best estimate” of indi-
    vidual dosage exposure, which was the average of the range.
    Rhodes now argues that this ruling was an abuse of discretion.
    [29] The district court has discretion to exclude evidence
    when its probative value is substantially outweighed by the
    danger of misleading the jury or confusing the issues. See
    FED. R. EVID. 403. This is especially true with respect to
    expert witnesses. Daubert, 
    509 U.S. at 595
    ; Daubert v. Mer-
    rell Dow Pharms., Inc., 
    43 F.3d 1311
    , 1321 n.17 (9th Cir.
    1995). In reviewing the record of the pre-trial hearing and the
    application of the “best estimate” testimony at both trials, the
    district court struck a fair balance between probative and mis-
    leading testimony. It allowed Dr. Hoffman to explain his con-
    fidence interval and to give a range of possible dosage
    exposure. It also helped the jury focus on the significance of
    such an interval, by having Dr. Hoffman highlight the average
    of the possible range. This ruling was not an abuse of discre-
    tion.
    E.   Cross-Examination of Dr. Hoffman.
    [30] The district court did not abuse its discretion in allow-
    ing Defendants to cross-examine Dr. Hoffman with testimony
    he gave at the first bellwether trial. At the first trial, Dr. Hoff-
    man testified to each plaintiff’s “probability of causation”
    (“PC”). Plaintiff Rhodes apparently decided that Dr. Hoff-
    man’s testimony on this issue was more harmful than helpful,
    and in a pre-trial motion for her second trial, she asked the
    court to exclude all references by either party to Dr. Hoff-
    IN RE: HANFORD NUCLEAR RESERVATION LITIGATION      9835
    man’s PC analysis. Rhodes, however, still wanted Dr. Hoff-
    man to testify on other topics.
    The district court properly denied the motion. Dr. Hoff-
    man’s testimony at the first bellwether trial was an admission
    of a party opponent under Federal Rule of Evidence
    801(d)(2)(C). Glendale Fed. Bank, FSB v. United States, 
    39 Fed. Cl. 422
    , 424-25 (1997). Plaintiff cannot now exclude
    trial testimony that she, herself, proffered. Defendants were
    properly permitted to cross-examine Dr. Hoffman on his pre-
    vious PC analysis.
    F.   Cross-Examination of Dr. Chopra.
    Rhodes next urges us to hold that the district court abused
    its discretion in allowing Defendants to use Dr. Hoffman’s PC
    analysis to cross-examine Dr. Chopra and impeach her credi-
    bility. We agree with Rhodes that this ruling was an abuse of
    discretion, but because the error had little or no effect on the
    verdict, there was no reversible error.
    Opposing counsel may cross-examine an expert on the facts
    or data on which his opinion was based. See FED. R. EVID.
    703; United States v. Preciado-Gomez, 
    529 F.2d 935
    , 942
    (9th Cir. 1976). Because Dr. Chopra did not rely on Dr. Hoff-
    man’s PC data, it should not have been admitted under that
    rule. See, e.g., Bryan, 566 F.2d at 547; Layton, 
    549 F. Supp. at 920
    ; Briggs v. Chi. G. W. R. Co., 
    57 N.W.2d 572
    , 583-84
    (Minn. 1953).
    Rhodes, however, does not show how the PC evidence
    could have materially affected the jury’s verdict. Defendants
    had already undermined Dr. Chopra’s credibility by highlight-
    ing the doctor’s lack of due diligence in uncovering Rhodes’
    medical history. There is no reason to believe that Defen-
    dants’ use of Dr. Hoffman’s testimony had any additional,
    much less, any substantial effect on the verdict.
    9836     IN RE: HANFORD NUCLEAR RESERVATION LITIGATION
    *     *      *
    [31] The jury’s defense verdict in Rhodes’ second trial
    must be affirmed.
    IX.    Conclusion.
    We are mindful of the time and resources both the district
    court and the parties have expended in this protracted litiga-
    tion. We also realize that resolution is needed. We affirm the
    district court’s major rulings. These relate to the government
    contractor defense, strict liability, and causation. We also
    affirm the district court’s ruling on the medical monitoring
    claims and the judgment against Plaintiff Rhodes, as well as
    the judgment in favor of Plaintiff Stanton. We reverse, on evi-
    dentiary grounds, the judgments against Plaintiffs Buckner,
    Carlisle, and Goldbloom, and on statute of limitations
    grounds, the judgment in favor of Plaintiff Wise. We remand
    those matters for further proceedings.
    Each party to bear its own costs on appeal.
    AFFIRMED IN PART; REVERSED AND REMANDED
    IN PART.