Gass v. Marriott Hotel Serv ( 2009 )


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    Pursuant to Sixth Circuit Rule 206
    File Name: 09a0078p.06
    UNITED STATES COURT OF APPEALS
    FOR THE SIXTH CIRCUIT
    _________________
    X
    Plaintiffs-Appellants, -
    ELIZABETH A. GASS, DEBORAH DEJONGE,
    -
    -
    -
    No. 07-1733
    v.
    ,
    >
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    MARRIOTT HOTEL SERVICES, INC., ECOLAB,
    Defendants-Appellees. -
    INC.,
    -
    N
    Appeal from the United States District Court
    for the Western District of Michigan at Grand Rapids.
    No. 05-00856—Robert Holmes Bell, District Judge.
    Argued: July 22, 2008
    Decided and Filed: March 3, 2009
    Before: BOGGS, Chief Judge; MOORE and CLAY, Circuit Judges.
    _________________
    COUNSEL
    ARGUED: Peter D. Bosch, STRAIN, MURPHY & VANDERWAL, Grand Rapids,
    Michigan, for Appellants. Richard G. Morgan, BOWMAN & BROOKE, Minneapolis,
    Minnesota, for Appellees. ON BRIEF: Peter D. Bosch, Joseph P. VanderVeen, STRAIN,
    MURPHY & VANDERWAL, Grand Rapids, Michigan, for Appellants. Ronald C. Wernette
    Jr., BOWMAN & BROOKE, Troy, Michigan, for Appellees.
    CLAY, J., delivered the opinion of the court, in which MOORE, J., joined. BOGGS,
    C. J. (pp. 23-31), delivered a separate dissenting opinion.
    _________________
    OPINION
    _________________
    CLAY, Circuit Judge. Plaintiffs, Elizabeth A. Gass and Deborah DeJonge, appeal
    the district court’s grant of summary judgment to Defendants, Ecolab, Inc. (“Ecolab”) and
    Marriott Hotel Services, Inc. (“Marriott”). Plaintiffs sued Defendants under Michigan law,
    claiming that they were poisoned by pesticides during their stay at a Marriott hotel in Maui,
    1
    No. 07-1733          Gass, et al. v. Marriott Hotel Servs., et al.                    Page 2
    Hawaii. Plaintiffs allege that employees of Ecolab, which provides extermination services
    for Marriott, sprayed their belongings with an unknown pesticide and filled their hotel room
    with toxic vapors, causing Plaintiffs to become ill. The district court granted summary
    judgment to Defendants, holding that no reasonable jury could conclude that Defendants’
    negligence caused Plaintiffs’ injuries. We disagree, and accordingly REVERSE the grant
    of summary judgment and REMAND this case to the district court for trial.
    BACKGROUND
    I.      FACTUAL HISTORY
    On September 6, 2004, Plaintiffs were guests in a Maui hotel operated by Marriott.
    That day, DeJonge filed a complaint with the hotel after she discovered a dead cockroach
    in her room, and a hotel employee eventually removed the roach. The next day, while
    Plaintiffs were away from their room, three employees of Ecolab entered Plaintiffs’ room,
    bringing with them at least one unidentified pesticide. Ecolab provides pest extermination
    services to Marriott.
    A.      Plaintiffs’ Exposure to Pesticides
    Although the parties offer opposing views of what happened while the Ecolab
    exterminators were in Plaintiffs’ hotel room, Defendants concede that the summary judgment
    standard requires this Court to credit Plaintiffs’ testimony regarding the exterminators’
    actions. According to Plaintiff DeJonge, she was relaxing on the beach with Plaintiff Gass
    when she decided to retrieve lunch money from the hotel room. DeJonge left the beach and
    walked to the ground-level hotel room, entering through a sliding glass door. Immediately
    upon entry, she discovered three men in the room. Two of the men were wearing metal tanks
    on their backs and masks on their faces, and were spraying a chemical from those tanks.
    According to DeJonge, there was a “thick, horrid, acrid putrid odor” in the room, and the air
    was “sort of cloudy.” (J.A. 490–91.) DeJonge also states that the haze of chemicals in the
    room was so thick that she could “see it, smell it, taste it, feel it.” (J.A. 494.)
    Upon noticing the three men, DeJonge immediately began screaming at the men to
    stop spraying, and accused them of “ruining [her] stuff,” much of which was laid out in
    suitcases on the floor. (J.A. 492–93.) In response to her demands, DeJonge testified that one
    No. 07-1733         Gass, et al. v. Marriott Hotel Servs., et al.                     Page 3
    of the men “shot [her] a dirty look,” yelled something in a language she did not understand,
    and resumed spraying. (J.A. 493.) At this point, DeJonge picked up the phone, called the
    hotel desk, and asked for the manager to meet her outside of the hotel room. She then left
    the room to wait for the manager.
    When the manager arrived, DeJonge relayed what had happened in the room, and
    demanded that they be given a new room immediately because “we need to get our stuff out
    of there before . . . it gets more ruined.” (J.A. 496.) DeJonge added that “I can’t stand the
    smell in there. I think it’s making me sick.” (Id.) The manager acquiesced, and called a
    bellhop to help DeJonge move her belongings to a new room. DeJonge then left to find Gass
    and let her know what happened.
    DeJonge found Gass and explained why they needed to retrieve their belongings and
    switch rooms. By the end of this conversation, which lasted about six or seven minutes,
    DeJonge began to feel ill. Nevertheless, both women returned to the room, where they spent
    about two-and-a-half minutes gathering their belongings. Neither DeJonge nor Gass
    identified the specific chemical that Ecolab used to fumigate their room.
    Although Defendants concede that the summary judgment standard requires that this
    Court accept Plaintiffs’ version of events, Defendants offer a different version of how the
    exterminators acted. According to testimony by Michael Medeiros, an Ecolab exterminator,
    he and one co-worker entered Plaintiffs’ room just thirty seconds before DeJonge arrived.
    According to Medeiros, neither Ecolab employee had sprayed any pesticides before DeJonge
    entered the room. Medeiros claims that his co-worker made “two quick squirts” of an
    insecticide from an aerosol can similar to those commercially available at retail stores, and
    that no other chemicals were sprayed in the room. (J.A. 481.) Medeiros further testified
    that, immediately after the exterminator made these “quick squirts,” DeJonge became “very
    upset,” and began yelling at Medeiros and his co-worker. (Id.) The two men left the room,
    and Medeiros claims that he heard DeJonge say “my stuff is ruined” as they were leaving.
    (Id.)
    Medeiros also testified regarding the kinds of chemicals Ecolab typically used in
    servicing the Marriott hotel, identifying three kinds of insecticides used to target
    cockroaches. The first, and least potent, of these chemicals is a pesticide called “SSI-50,”
    No. 07-1733              Gass, et al. v. Marriott Hotel Servs., et al.                           Page 4
    which is normally sprayed from a twelve-ounce aerosol can. Additionally, Medeiros
    identified two more-potent pesticides—“Suspend SC” and “Demand CS”—that were
    commonly used by Ecolab at the time of Plaintiffs’ trip to Hawaii. Suspend SC and Demand
    CS are sold in concentrated form, then mixed with water in a pump sprayer or similar
    container to apply the pesticide. Medeiros claims that, on September 7, 2004, the day
    Plaintiffs’ room was sprayed, only SSI-50 was used, and a report he filed that day
    corroborates his claim.
    B.       Plaintiffs’ Illness
    A short time after their exposure to pesticides in the hotel room, Plaintiffs contacted
    the hotel manager and complained of “numbness to their tongues, stomach aches, and seeing
    stars.” (J.A. 370.) The manager arranged transportation to a nearby urgent care center, and
    Plaintiffs received medication for their symptoms.
    Upon their return to Michigan, Plaintiffs initially sought treatment from Dr. Robert
    1
    DeJonge, an osteopathic physician and Plaintiff DeJonge’s husband.                     Dr. DeJonge,
    however, eventually referred Plaintiffs to Dr. Gerald Natzke, a physician specializing in
    environmental medicine.2 During her appointment with Dr. Natzke on October 19,
    2004, DeJonge informed Dr. Natzke that she had developed various symptoms within
    fifteen minutes of her exposure to the pesticides, including “a headache, swelling of her
    tongue, hands, feet and face, profuse itching, dizziness, shortness of breath and . . .
    drooling.” (J.A. 846.) By the time of her appointment, DeJonge’s symptoms included
    “a slurring and swollen tongue, complaints of a foul taste in her mouth, drooling and
    complaints of fatigue and pain in her muscles and joints,” in addition to a need to “take
    afternoon naps which wasn’t the case before the incident on September 7, 2004[,] . . .
    diarrhea and [] a droopy left eye.” (Id.)
    1
    Unless otherwise indicated, “DeJonge” will refer to Ms. DeJonge, not Dr. DeJonge.
    2
    Physicians specializing in environmental medicine treat “adverse reactions experienced by an
    individual on exposure to an environmental excitant,” such as a pesticide. See American Academy of
    Environmental Medicine, What Is Environmental Medicine?, http://www.aaemonline.org/introduction.html
    (last visited August 11, 2008).
    No. 07-1733        Gass, et al. v. Marriott Hotel Servs., et al.                    Page 5
    Gass had her first appointment with Dr. Natzke on October 22, 2004, and
    complained of “achiness all over, chills, sweats, fever, blisters on her tongue, droopiness
    on the right side of her face, muscle spasms, dizziness, blurred vision and memory
    problems.” (J.A. 847.) Like DeJonge, Gass told Dr. Natzke that within ten to fifteen
    minutes of her exposure to the pesticides, she developed “weakness and fatigue and had
    a green/gray tongue which she said turned black about 1½ weeks later.” (Id.)
    According to Dr. Natzke, both women also exhibited neurological symptoms,
    including “brain fog, memory loss [and] mood swings.” (J.A. 848.) He administered
    a “visual contrast sensitivity test” to Gass, which Dr. Natzke said “she failed miserably”
    and had “one of the worst test results I have seen.” (Id.) Gass’ poor performance on the
    vision test indicated to Dr. Natzke “that she was exposed to neurotoxins.” (Id.) Dr.
    Natzke added that “[a]ll pesticides contain neurotoxins.” (Id.) Dr. Natzke also noted
    that both women “exhibited black tongues” at some point since he began treating them,
    a symptom that he attributed to pesticides in their system. (Id.)
    Based on their symptoms, Dr. Natzke diagnosed both DeJonge and Gass with
    “acute pesticide exposure.” (J.A. 846–47.) However, he could not identify the particular
    pesticide to which Plaintiffs were exposed. Although a test for pyrethroids and other
    chemical compounds found in SSI-50 (the least potent of the three pesticides purportedly
    used at the Marriott in Maui) did not reveal “detectable levels” of such compounds in
    Plaintiffs’ systems, Dr. Natzke did not rule out the possibility that Gass and DeJonge
    were exposed to SSI-50 because “the concentration of chemicals from the pesticide
    contamination . . . would have been diluted in their blood by the time I saw them in mid-
    October.” (J.A. 847.) Dr. Natzke did not test Plaintiffs for other toxins because “there
    are tens of thousands of chemicals and it is impossible to test for all such chemicals
    without specifically knowing what chemical a person was exposed to.” (Id.)
    No. 07-1733           Gass, et al. v. Marriott Hotel Servs., et al.                              Page 6
    C.       Defendants’ Experts
    Despite the uncertainty regarding which toxin or toxins Plaintiffs were exposed
    to, Defendants introduced substantial expert testimony indicating that SSI-50 could not
    have caused the symptoms experienced by Plaintiffs. First, Defendants point to a report
    by Marcia van Germert, Ph.D., a toxicologist with a doctorate in Pharmacology and
    Biochemistry. Although Dr. van Germert did not examine the toxic effects of any
    substance other than SSI-50, she concludes that “no peer reviewed study” demonstrates
    that the chemicals in SSI-50 have “ever produced a toxic effect in humans, or produced
    the symptoms alleged by the plaintiffs” when those chemicals are used merely for
    “crack and crevice application.” (J.A. 180.)
    Similarly, the record contains a report by H. James Wedner, MD, chief of the
    Division of Allergy and Immunology Medicine of the Washington University School of
    Medicine. According to Dr. Wedner, “throughout the ages there have been individuals
    who have developed conditions that have defied characterization.” (J.A. 196.) Dr.
    Wedner suggests that Plaintiffs may be suffering from such a condition which “do[es]
    not seem to have an obvious cause.” (Id.) Nevertheless, Wedner concluded that neither
    Gass nor DeJonge “suffered any health problems that are related to their potential
    exposure to Ssi-50 [sic] in their hotel room in Maui on September 7, 2004.” (J.A. 191.)
    Dr. Wedner provides no analysis regarding the possible effect of Suspend SC, Demand
    CS, or any other pesticide on Plaintiffs.3
    Finally, the record contains a report by Elissa P. Benedek, MD, a clinical
    psychiatrist who holds faculty appointments at three universities. Dr. Benedek attempts
    to dismiss Plaintiffs’ symptoms as merely psychosomatic, concluding that both DeJonge
    and Gass have “demonstrated a tendency to react to stress in the past with physical
    symptoms, and now continue[] to react to psychological stressors with physical
    3
    The record also contains a report from Dr. Gary Bennett, an Entomology professor at Purdue
    University. After surveying the legal landscape governing pesticide use, Dr. Bennett ultimately concludes
    that “Ecolab’s treatment was proper, including the selection of products, and the treatment method and
    amount of product used.” (J.A. 129.) It is unclear from Dr. Bennett’s report, however, what the basis of
    his conclusions might be.
    No. 07-1733         Gass, et al. v. Marriott Hotel Servs., et al.                   Page 7
    symptoms and complaints.” (J.A. 225, 242) According to Dr. Benedek, Gass and
    DeJonge’s symptoms resulted from nothing more than a psychological reaction to stress.
    II.     PROCEDURAL HISTORY
    Plaintiffs filed this diversity case in the Western District of Michigan on
    December 29, 2005, alleging that Defendants negligently exposed them to pesticides and
    that this exposure was the cause of their subsequent illness. After discovery, Defendants
    moved for summary judgment. On May 8, 2007, the district court granted Defendants’
    motion for summary judgment. This appeal followed.
    DISCUSSION
    I.      CHOICE OF LAW
    Federal courts sitting in diversity apply the choice of law provisions of the forum
    state. NILAC Int’l Mktg. Group v. Ameritech Servs., Inc., 
    362 F.3d 354
    , 358 (6th Cir.
    2004). Because Plaintiffs filed this case in the Western District of Michigan, Michigan
    choice of law provisions apply. 
    Id.
    Michigan choice of law provisions favor allowing Michigan residents to bring
    suit in Michigan courts under Michigan law. See Olmstead v. Anderson, 
    400 N.W.2d 292
    , 302–03 (Mich. 1987). Generally speaking, a tort claim filed in a Michigan court
    will be governed by Michigan law “unless a ‘rational reason’ exists to displace it.”
    Watkins & Son Pet Supplies v. Iams Co., 
    254 F.3d 607
    , 611 (6th Cir. 2001) (quoting
    Olmstead, 400 N.W.2d at 305). Moreover, the fact that a tort took place outside of
    Michigan is not itself a sufficient reason to apply a different state’s law. See Olmstead,
    400 N.W.2d at 302 (holding that the fact that an accident occurred outside of Michigan
    is of no “great or particular significance” in determining which state’s law to apply in
    a tort suit). Additionally, although Michigan courts recognize that applying Michigan
    law rather than the law of the state in which the tort allegedly took place might lead to
    forum shopping, “[t]here is no forum-shopping concern when the forum is also the
    plaintiff’s state of citizenship.” Id. at 303.
    No. 07-1733         Gass, et al. v. Marriott Hotel Servs., et al.                   Page 8
    Plaintiffs are Michigan residents, and they present no arguments why the law of
    Hawaii or any other state should apply. Accordingly, we see no reason to displace
    Michigan’s presumption that Michigan substantive law governs tort suits brought within
    its borders. See id. at 302–03. However, under Erie Railroad Co. v. Tompkins, 
    304 U.S. 64
     (1938), federal law governs procedural issues, including evidentiary rulings made
    pursuant to the Federal Rules of Evidence. Legg v. Chopra, 
    286 F.3d 286
    , 289 (6th Cir.
    2002).
    II.      THE ADMISSIBILITY OF PLAINTIFFS’ EXPERTS’ TESTIMONY
    A.       Standard of Review
    We review a district court’s ruling regarding the admissibility of expert
    testimony for abuse of discretion. Aetna Cas. & Sur. Co. v. Leahey Constr. Co., 
    219 F.3d 519
    , 544 (6th Cir. 2000). “In the context of an evidentiary ruling, abuse of
    discretion exists when the reviewing court is firmly convinced that a mistake has been
    made regarding admission of evidence.” 
    Id.
     (quoting Polk v. Yellow Freight Sys., Inc.,
    
    876 F.2d 527
    , 532 (6th Cir. 1989)).
    B.       Analysis
    As a threshold matter, Plaintiffs contest the district court’s decision to exclude
    statements by Dr. DeJonge and Dr. Natzke as unreliable opinion testimony. Generally,
    a treating physician may provide expert testimony regarding a patient’s illness, the
    appropriate diagnosis for that illness, and the cause of the illness. See Fielded v. CSX
    Transp., Inc., 
    482 F.3d 866
    , 870 (6th Cir. 2007). However, a treating physician’s
    testimony remains subject to the requirement set forth in Daubert v. Merrell Dow
    Pharmaceuticals, 
    509 U.S. 579
     (1993), that an expert’s opinion testimony must “have
    a reliable basis in the knowledge and experience of his discipline.” 
    Id. at 592
    . Under
    Daubert, before allowing an expert’s testimony to be considered by the jury, a trial court
    should consider: (1) whether the reasoning or methodology underlying the expert’s
    testimony is scientifically valid; and (2) whether that reasoning or methodology properly
    No. 07-1733            Gass, et al. v. Marriott Hotel Servs., et al.                                Page 9
    could be applied to the facts at issue to aid the trier of fact.” United States v. Smithers,
    
    212 F.3d 306
    , 315 (6th Cir. 2000).
    In assessing whether Dr. DeJonge and Dr. Natzke’s testimony satisfies the
    requirements of Daubert, the district court concluded that Dr. DeJonge and Dr. Natzke
    could testify as to Plaintiffs’ “symptoms, tests, diagnosis, and treatment.” Gass v.
    Marriott Hotel Servs., Inc., 
    501 F. Supp. 2d 1011
    , 1021 (W.D. Mich. 2007). The district
    court determined that both doctors “are experienced physicians and are qualified to
    diagnose medical conditions and treat patients.” 
    Id. at 1019
    . However, with respect to
    the doctors’ “causation opinions,” the district court concluded that “Dr. Natzke and Dr.
    DeJonge have not demonstrated a scientifically reliable method to support their
    conclusions as to causation in this particular matter and may not be permitted to testify
    as to the cause of Plaintiffs’ symptoms.” 
    Id. at 1021
    . The district court reasoned that
    “[t]he ability to diagnose medical conditions is not remotely the same . . . as the ability
    to deduce, delineate, and describe, in a scientifically reliable manner, the causes of those
    medical conditions.” 
    Id. at 1019
     (quoting Wynacht v. Beckman Instruments, Inc., 
    113 F. Supp. 2d 1205
    , 1209 (E.D. Tenn. 2000)). Because “Dr. Natzke and Dr. DeJonge have
    not based their causation opinions on any testing data,” and the only blood tests which
    Dr. Natzke relied on “did not reveal any detectable levels for the products the lab tested
    for,” the district court found that neither physician had a scientific basis for their
    “causation opinion.” Id. at 1019, 1021.4
    Insofar as the district court permitted Dr. DeJonge and Dr. Natzke to offer a
    diagnosis, while excluding testimony on matters outside of their professional experience,
    the district court’s decision is similar to Dickenson v. Cardiac & Thoracic Surgery of
    4
    While the district court’s decision to exclude the doctors’ “causation opinion” could be seen as
    inconsistent with its decision to allow the doctors to testify regarding their diagnosis of Plaintiffs’
    condition as acute pesticide exposure, the district court’s conclusions likely recognize that, although both
    doctors are competent to testify regarding Plaintiffs’ diagnosis (even if the diagnosis necessarily implies
    exposure to pesticides), neither doctor is competent to testify regarding the specific pesticide and the time
    frame of exposure. The district court emphasized that neither doctor engaged in testing that revealed the
    particular pesticide Plaintiffs were exposed to, and neither doctor “referenced any scientific literature
    establishing a connection between Plaintiffs’ exposure to some unknown pesticide and symptoms that they
    continue to experience over two years after the exposure.” Gass, 
    501 F. Supp. 2d at 1020
    . Thus, the
    district court ruled that while Dr. Natzke and Dr. DeJonge are competent to testify that Plaintiffs are
    suffering from pesticide exposure, neither is competent to testify regarding whether Defendants caused this
    exposure.
    No. 07-1733        Gass, et al. v. Marriott Hotel Servs., et al.                  Page 10
    Eastern Tenn., P.C., 
    388 F.3d 976
     (6th Cir. 2004). In Dickenson, we considered the
    expert testimony of Dr. Johnson, a cardiac surgeon, regarding the cause of a patient’s
    brain injuries. Dr. Johnson testified that the patient’s injuries resulted from premature
    removal of her ventilation tube, 
    id. at 978-79
    , and that the patient’s cardiac surgeon was
    responsible for the decision to prematurely extubate the patient, 
    id. at 982
    . In holding
    that Dr. Johnson could testify that the patient suffered injuries as a result of premature
    extubation, the court in Dickenson disagreed with the district court’s conclusion that,
    because Dr. Johnson was neither a pulmonologist nor familiar with scholarly literature
    in the field of pulmonology, he was not qualified to provide expert testimony regarding
    whether the patient should have been extubated. 
    Id. at 980
    .
    According to Dickenson, a physician need not “demonstrate a familiarity with
    accepted medical literature or published standards in [an area] of specialization in order
    for his testimony to be reliable in the sense contemplated by Federal Rule of Evidence
    702.” 
    Id.
     Rather, “the text of Rule 702 expressly contemplates that an expert may be
    qualified on the basis of experience.”       
    Id.
     (quoting Fed. R. Evid. 702 advisory
    committee’s note); see also Kumho Tire Co., Ltd. v. Carmichael, 
    526 U.S. 137
    , 156
    (1999) (“[N]o one denies that an expert might draw a conclusion from a set of
    observations based on extensive and specialized experience.”). The exclusion of a
    medical doctor’s professional opinion, rooted in that doctor’s “extensive relevant
    experience,” is “rarely justified in cases involving medical experts as opposed to
    supposed experts in the area of product liability.” Dickenson, 
    388 F.3d at 982
    . Because
    Dr. Johnson stated in his affidavit that he is “involved with extubation decisions on
    almost a daily basis,” the court concluded that his significant experience qualified him
    to testify as to whether another physician prematurely extubated a patient. 
    Id. at 978
    .
    The court in Dickenson reached the opposite conclusion with respect to Dr.
    Johnson’s testimony that the patient’s cardiac surgeon—as opposed to the patient’s
    pulmonologist—was at fault for the decision to prematurely extubate the patient. 
    Id. at 982
    . The court reasoned that there was no support for Dr. Johnson’s opinion that the
    patient’s cardiac surgeon was at fault for the premature extubation because Dr. Johnson
    No. 07-1733        Gass, et al. v. Marriott Hotel Servs., et al.                  Page 11
    testified to nothing in his experience which supported his theory that the cardiac surgeon
    was somehow responsible for the pulmonologist’s decision. Thus, Dickenson stands for
    the proposition that a medical doctor is generally competent to testify regarding matters
    within his or her own professional experience. See 
    id. at 982
    . When, however, the
    doctor strays from such professional knowledge, his or her testimony becomes less
    reliable, and more likely to be excluded under Rule 702. See 
    id.
     at 982–83.
    In light of this reading of Dickenson, we believe that the district court did not
    abuse its discretion. Both Dr. DeJonge and Dr. Natzke relied on professional experience
    in diagnosing and treating Plaintiffs. Specifically, Dr. Natzke stated in an affidavit that
    he relied on his experience treating “thousands of patients for environmental medicine
    issues including pesticide and/or other chemical contamination.” (J.A. 846.) Under
    Dickenson, both Dr. DeJonge and Dr. Natzke are competent to testify with respect to
    Plaintiffs’ diagnosis to the extent that they rely on professional education or experience.
    See 
    388 F.3d at 982
    . Conversely, nothing in Dr. DeJonge’s or Dr. Natzke’s medical
    expertise would provide a basis to determine the exact chemical Plaintiffs were exposed
    to at the Marriott hotel. In addition, because Defendants did not disclose that Plaintiffs
    possibly were exposed to Demand CS or Suspend SC until very late in the discovery
    process, the doctors could not run tests to determine whether Plaintiffs actually were
    exposed to such chemicals, which would have provided a basis for the doctors’ causation
    opinion. Accordingly, similar to the expert witness in Dickenson who lacked a basis in
    experience or personal knowledge regarding which doctor made the decision to
    prematurely extubate a patient and, as a result, could not testify regarding which doctor
    ordered the extubation, 
    id.,
     Dr. DeJonge and Dr. Natzke cannot rely on their general
    knowledge of pesticides to testify regarding the specific pesticide that caused Plaintiffs’
    symptoms, or when Plaintffs’ exposure to that pesticide occurred.
    The district court correctly permitted Dr. DeJonge and Dr. Natzke to testify
    regarding their diagnosis of Plaintiffs, and properly excluded their testimony regarding
    where and when Plaintiffs were exposed to pesticides. Therefore, the district court did
    No. 07-1733        Gass, et al. v. Marriott Hotel Servs., et al.                  Page 12
    not abuse its discretion in limiting Dr. DeJonge and Dr. Natzke’s testimony to matters
    within their professional experience or personal knowledge.
    III.   THE DISTRICT COURT’S GRANT OF SUMMARY JUDGMENT
    A.     Standard of Review
    The district court granted summary judgment to Defendants with respect to
    Plaintiffs’ negligence claims. Gass, 
    501 F. Supp. 2d at 1026
    . A district court’s grant of
    summary judgment is reviewed de novo. Farhat v. Jopke, 
    370 F.3d 580
    , 587 (6th Cir.
    2004). The district court’s grant of summary judgment should be affirmed when “the
    discovery and disclosure materials on file, and any affidavits show that there is no
    genuine issue as to any material fact” as to an essential element of the non-moving
    party’s case. Fed. R. Civ. P. 56(c). An issue of fact is “genuine” if a reasonable person
    could return a verdict for the non-moving party. Anderson v. Liberty Lobby, Inc., 
    477 U.S. 242
    , 248 (1986). After the moving party has satisfied its burden, the burden shifts
    to the non-moving party to set forth “specific facts showing that there is a genuine issue
    for trial.” Matsushita Elec. Indus. Co. v. Zenith Radio Corp., 
    475 U.S. 574
    , 587 (1986).
    When no genuine issues of material fact exist, this Court reviews de novo the district
    court’s conclusions of substantive law. Farhat, 
    370 F.3d at 588
    .
    B.     Analysis
    Plaintiffs argue that the district court erred in granting summary judgment to
    Defendants on the grounds that, absent expert testimony linking Plaintiffs’ symptoms
    to a particular pesticide, no reasonable jury could have found that Defendants
    negligently caused Plaintiffs’ illness. We agree.
    We first emphasize that, in deciding a motion for summary judgment, we must
    draw all justifiable inferences in favor of Plaintiffs as the non-moving party, and
    “[Plaintiffs’] evidence is to be believed.” Martin v. Toledo Cardiology Consultants,
    Inc., 
    548 F.3d 405
    , 410 (6th Cir. 2008) (citing Liberty Lobby, 
    477 U.S. at 255
    ).
    According to Plaintiff DeJonge, she returned to her hotel room to find men in masks
    spraying chemicals. She testified that there was a “thick, horrid, acrid putrid odor” in
    No. 07-1733        Gass, et al. v. Marriott Hotel Servs., et al.                  Page 13
    the room, and that the air was “sort of cloudy.” (J.A. 490–91.) The haze of chemicals
    in the room was so thick that she could “see it, smell it, taste it, feel it.” (J.A. 494.)
    Within fifteen minutes of her exposure to the “cloud,” DeJonge claims that she became
    ill. Similarly, Plaintiff Gass testified that she began to experience symptoms shortly
    after her exposure to the cloud of pesticides in the hotel room. We conclude that, should
    a jury credit Plaintiffs’ testimony and the other evidence supporting Plaintiffs’ claim, a
    reasonable jury could find that Defendants are liable for causing Plaintiffs’ injuries.
    Plaintiffs claim that Defendants’ negligence caused their illnesses. Accordingly,
    as in any case alleging simple negligence under Michigan law, Plaintiffs must
    demonstrate: “(1) that defendant owed them a duty of care, (2) that defendant breached
    that duty, (3) that plaintiffs were injured, and (4) that defendant’s breach caused
    plaintiffs’ injuries.” Henry v. Dow Chem. Co., 
    701 N.W.2d 684
    , 688 (Mich. 2005).
    Defendants argue on appeal, and the district court held, that Plaintiffs have failed to
    demonstrate both that Defendants breached a duty of care and that such a breach caused
    Plaintiffs’ injuries. We consider each of these arguments below.
    1.      Duty of Care
    Defendants characterize Plaintiffs’ negligence claim as an allegation that
    Defendants violated the professional standard of care governing exterminators, and
    therefore conclude that Plaintiffs’ claim must fail because Plaintiffs failed to present
    expert testimony to establish the standard of care applicable to exterminators. The
    dissent agrees and, although it acknowledges that the case is “not a ‘professional care’
    case,” Dissenting Op. at 26, it argues that, “[i]n Michigan, expert testimony in
    professional negligence (and toxic tort) cases like this one is required to avoid summary
    judgment . . . ,” 
    id.
     However, Michigan law does not require expert testimony under the
    circumstances presented in this case. The cases the dissent cites, such as Lince v.
    Monson, 
    108 N.W.2d 845
     (Mich. 1961), address medical malpractice claims against, for
    example, a surgeon performing a complex medical procedure, not an exterminator
    spraying pesticides.
    No. 07-1733        Gass, et al. v. Marriott Hotel Servs., et al.                  Page 14
    The dissent also asserts that “these cases require expert testimony in complex,
    professional, or scientific-based negligence cases.” Dissenting Op. at 26. While the
    dissent’s statement is literally true—medical malpractice cases do involve “complex,
    professional, and scientific-based” questions—the dissent’s use of such cases to require
    Plaintiffs to produce expert testimony under the circumstances is entirely misleading.
    In the medical malpractice context, as demonstrated by the cases the dissent relies on,
    the applicable standard of care generally is “beyond the ken of laymen.” Thomas v.
    McPherson Cmty. Health Ctr., 
    400 N.W.2d 629
    , 705 (Mich. Ct. App. 1986). As a result,
    “in an action for malpractice against a hospital, expert testimony is required to establish
    the applicable standard of conduct, the breach of that standard, and causation.” 
    Id.
     As
    the Michigan Supreme Court has recognized, proving negligence and causation in
    medical malpractice cases is different than in ordinary negligence cases. In a case
    involving “conduct, like that of a surgeon, resting upon judgment, opinion, or theory, the
    ordinary rules for determining negligence do not prevail.” Lince, 108 N.W.2d at 848
    (internal quotation marks omitted) (citation omitted). Pervasively spraying pesticides
    within an enclosed room inhabited by humans, however, is not “conduct . . . resting upon
    judgment, opinion, or theory,” and is not a “matter[] of special knowledge strictly
    involving professional skill.” Id. Although Michigan courts require plaintiffs to produce
    an expert in medical malpractice cases to explain the applicable standard of care,
    Michigan law does not require Plaintiffs to present expert testimony regarding the
    standard of care applicable to spraying chemicals in the confined quarters of an occupied
    room.
    Accordingly, Plaintiffs’ claim in the present case that Defendants negligently
    sprayed pesticides is more akin to an ordinary negligence case than a claim involving
    professional negligence. The dissent’s attempt to classify Plaintiffs’ claim as one
    involving professional negligence is not supported by Michigan case law. Thus, even
    in the absence of expert testimony regarding “how the room should have been sprayed
    or how the risk of chemical poisoning should have been reduced,” Dissenting Op. at 25,
    Michigan law does not prevent Plaintiffs from avoiding summary judgment in the
    No. 07-1733        Gass, et al. v. Marriott Hotel Servs., et al.                  Page 15
    absence of expert testimony where the factfinder is able to weigh and evaluate the
    evidence based on his or her ordinary experience.
    Through their testimony, Plaintiffs allege that men in masks entered their hotel
    room and, despite the presence of Plaintiffs’ suitcases and similar indications that the
    room was in use, sprayed such a thick concentration of pesticides that a “thick, horrid,
    acrid[,] putrid” cloud of toxic chemicals filled the room. (J.A. 490.) Expert testimony
    is not necessary to allow a reasonable jury to conclude that such actions are negligent,
    inasmuch as an ordinary person understands that it is unacceptable to enter a place where
    another is residing and fill that place with airborne poison, without providing for
    evacuation of the inhabitants, appropriate ventilation, or taking other precautions.
    Plaintiffs also have introduced evidence indicating that Defendants were aware
    of potential injuries that result from contact with at least two of the pesticides commonly
    used in exterminating cockroaches. By federal regulation, manufacturers of hazardous
    chemicals must produce a “material safety data sheet” (“MSDS”), and employers using
    such chemicals must keep a copy of the MSDS for each chemical that they use. 
    29 C.F.R. § 1910.1200
    (g)(1). Each MSDS must detail “[t]he health hazards of the
    hazardous chemical, including signs and symptoms of exposure, and any medical
    conditions which are generally recognized as being aggravated by exposure to the
    chemical.” § 1910.1200(g)(2)(iv). According to the MSDS for Suspend SC, one of the
    pesticides used by Defendants, Suspend SC is “[h]armful if inhaled,” and the MSDS
    warns that a person who does inhale the product should be “remove[d] to fresh air” and
    given “medical attention.” (J.A. 527.) The MSDS for Demand CS offers even more
    serious warnings, instructing persons who may come in contact with the pesticide to
    wear protective clothing to avoid “[u]nprotected contact” with the chemical, and to
    either ensure that areas where Demand CS is being applied are well-ventilated or to have
    persons in the area wear respirators. (J.A. 535.) Indeed, mere skin contact with Demand
    CS is dangerous, and the MSDS for this pesticide warns that if the pesticide gets on a
    person’s skin or clothing, that person should “[t]ake off contaminated clothing,” [r]inse
    No. 07-1733        Gass, et al. v. Marriott Hotel Servs., et al.                  Page 16
    skin immediately with plenty of water for 15-20 minutes,” and “[c]all [the
    manufacturer], a poison control center or doctor for treatment advice.” (J.A. 534.)
    A reasonable person would understand that he or she could seriously injure
    another person by filling an occupied hotel room with a cloud of toxic or hazardous
    chemicals. Based on this fact, and the evidenced introduced by Plaintiffs indicating that
    Defendants were aware that at least some of the chemicals they routinely use could cause
    serious illness, a jury reasonably could find that Defendants were negligent in inundating
    an occupied hotel room with pesticide spray in the absence of any warnings to the
    occupants. Accordingly, the district court erred in granting summary judgment to
    Defendants on the ground that Plaintiffs failed to introduce expert testimony establishing
    that Defendants breached a duty of care.
    2.      Causation
    Defendants offer two arguments supporting their belief that no reasonable jury
    could find that the chemicals Plaintiffs allegedly were exposed to caused their illness.
    First, Defendants argue that, because Plaintiffs do not know exactly which chemical they
    were exposed to, a reasonable jury could not conclude that they were exposed to a
    chemical, dispensed by these Defendants, which could have caused their particular
    symptoms. Additionally, Defendants claim that expert testimony is required to establish
    causation. Neither of these claims has merit.
    Defendants use three different chemicals to exterminate cockroaches at the
    Marriott in Maui: SSI-50, Demand CS, and Suspend SC, and Defendants admit that
    exterminators were in Plaintiffs’ hotel room in response to Plaintiffs’ earlier complaint
    of a dead cockroach in the room. Nevertheless, Defendants argue—without citing any
    cases—that, because Plaintiffs do not know exactly which chemical they were exposed
    to, “as a matter of law they cannot competently establish that such a mystery substance
    caused their claimed ailments.” (Def.’s Br. 39.)
    Michigan law, however, requires only that a plaintiff claiming negligence prove
    his or her case by a preponderance of the evidence, and does not require that a plaintiff
    No. 07-1733         Gass, et al. v. Marriott Hotel Servs., et al.                   Page 17
    alleging exposure to a harmful substance prove with certainty that he or she was exposed
    to a particular chemical. See Liberty Mut. Ins. Co. v. Bay City, Water Dept., 
    116 N.W.2d 199
    , 200 (Mich. 1962). Therefore, Plaintiffs may survive summary judgment if a
    reasonable jury could find that it is more likely than not that Defendants caused Plaintiffs
    to be exposed to a sufficient quantity of a hazardous substance capable of causing their
    injuries.
    Although Defendants introduced substantial expert testimony indicating that
    exposure to SSI-50 could not have caused Plaintiffs’ illness, they declined to offer any
    evidence regarding the toxic properties of Demand CS and Suspend SC. While the
    record contains little evidence regarding the toxic effects of Suspend SC, based on the
    MSDS for Demand CS, a reasonable jury could conclude that Demand CS is capable of
    producing many of the symptoms experienced by Plaintiffs, especially because
    Defendants failed to introduce any evidence rebutting the MSDS’s description of
    Demand CS as a highly dangerous toxin capable of causing a myriad of symptoms.
    According to Dr. Natzke, Plaintiff DeJonge experienced a wide range of
    symptoms, including “a headache, swelling of her tongue, hands, feet and face, profuse
    itching, dizziness, shortness of breath . . . a slurring and swollen tongue, complaints of
    a foul taste in her mouth, drooling and complaints of fatigue and pain in her muscles and
    joints,” in addition to a need to “take afternoon naps which wasn’t the case before the
    incident on September 7, 2004 . . . diarrhea and [] a droopy left eye.” (J.A. 846.)
    Plaintiff Gass experienced “achiness all over, chills, sweats, fever, blisters on her tongue,
    droopiness on the right side of her face, muscle spasms, dizziness, blurred vision and
    memory problems . . . weakness and fatigue and [] green/gray tongue which she said
    turned black about 1½ weeks later.” (J.A. 847.)
    The MSDS for Demand CS warns that it can cause many of these symptoms,
    including “central nervous system depression,” “irritation to eyes, skin and respiratory
    tract,” “headaches, dizziness, anesthesia, drowsiness . . . and other central nervous
    system effects.” (J.A. 536.) Moreover, according to the MSDS, the chemicals in
    Demand CS target the liver, nervous system, kidney, blood, respiratory tract, skin and
    No. 07-1733        Gass, et al. v. Marriott Hotel Servs., et al.                  Page 18
    eye. Although the MSDS does not account for all of Plaintiffs’ symptoms, such as their
    discolored tongues, Dr. Natzke stated in his affidavit that this symptom could be
    attributed to pesticide poisoning.
    Accordingly, viewing the evidence in the light most favorable to Plaintiffs as the
    non-moving parties, a reasonable jury could find that Plaintiffs’ symptoms were caused
    by their exposure to the pesticides sprayed by Defendants. Plaintiffs have produced
    ample evidence to demonstrate that at least one of the chemicals Defendants routinely
    used to exterminate cockroaches, Demand CS, is capable of causing their symptoms.
    Plaintiffs further have testified that they were exposed to a visible and pungent cloud of
    pesticides after Defendants sprayed pesticides in their room while Plaintiffs occupied the
    room. It is also significant that Plaintiffs began experiencing symptoms within fifteen
    minutes of their alleged exposure to pesticides in their hotel room. In addition,
    Defendants have offered no evidence to refute the MSDS’s representation of Demand
    CS as a chemical which could have caused Plaintiffs’ symptoms.
    Despite this evidence, Defendants argue that this Court’s decision in Kalamazoo
    River Study Group v. Rockwell International Corp., 
    171 F.3d 1065
     (6th Cir. 1999),
    requires Plaintiffs to introduce an “essential element” of “admissible expert testimony”
    in order to prove causation. That case, however, cannot be read so broadly. Kalamazoo
    River was an environmental contamination case, involving 38 miles of shoreline which
    was polluted by the chemical polychorinated biphenyl (“PCB”). 
    Id. at 1066
    . The
    defendant in Kalamazoo River owned an automotive parts manufacturing plant, located
    3200 feet from an entry into the tainted waterways, which leaked PCB into the
    surrounding soil in 1989. 
    Id. at 1067
    . In 1993, the defendant, acting with the approval
    of state environmental authorities, undertook to repair any environmental damage caused
    by the 1989 leak. As a result of these efforts, the defendant excavated approximately
    800 cubic yards of soil from the area surrounding the leak, and conducted soil studies
    revealing that PCB had traveled no farther then 1400 feet away from the site leak—1800
    feet short of the nearby waterway. 
    Id. at 1067, 1069
    . Nevertheless, in 1995, the
    No. 07-1733         Gass, et al. v. Marriott Hotel Servs., et al.                 Page 19
    defendant was named in the Kalamazoo River lawsuit, which alleged that the 1989 leak
    had contributed to the PCB contamination along the 38 miles of shoreline. 
    Id. at 1067
    .
    In holding that the defendant could not be held liable for the PCB contamination
    along the shoreline, the court noted that the plaintiff presented no reliable expert
    testimony which refuted evidence showing that PCB from the 1989 leak never reached
    the nearby waterway. 
    Id.
     at 1072–73. Accordingly, the court held that, “[t]he analytical
    gap between the evidence presented [by the plaintiff] and the inferences to be drawn
    . . . is too wide. Under such circumstances, a jury should not be asked to speculate on the
    issue of causation.” 
    Id. at 1073
     (quoting Turpin v. Merrell Dow Pharms., Inc., 
    959 F.2d 1349
    , 1360–61 (6th Cir. 1992)).
    Contrary to Defendants’ assertions, the principle governing Kalamazoo River is
    not applicable to Plaintiffs’ claims. Unlike in Kalamazoo River, where the defendant
    presented scientific evidence affirmatively demonstrating that it was not responsible for
    any PCB contamination along the shoreline, Defendants have presented nothing more
    than   statements    by    their   own    agent—an       exterminator   who   works    for
    Defendants—claiming that neither Demand CS nor a similarly toxic chemical was used
    in Plaintiffs’ hotel room. In other words, while the Kalamazoo River defendant proved
    an absence of causation by introducing objectively verifiable scientific evidence,
    Defendants have not done so. Though it is certainly reasonable, as this Court held in
    Kalamazoo River, 
    171 F.3d at
    1072–73, to require a party to refute scientific evidence
    with scientific evidence, Plaintiffs are not required to produce expert testimony on
    causation where Defendants have failed to offer scientific evidence regarding the effects
    of Demand CS or Suspend SC.
    The complexity of the factual issue presented in Kalamazoo River also justified
    requiring the plaintiff to support its case with expert testimony. Kalamazoo River
    concerned whether a 1989 chemical spill, allegedly cleaned up in 1993, traveled through
    3200 feet of soil to a nearby waterway, and then spread out along 38 miles of shoreline.
    
    Id.
     at 1066–67. Such an inquiry is beyond the capacity of twelve lay people, absent
    some assistance from an expert.
    No. 07-1733             Gass, et al. v. Marriott Hotel Servs., et al.                           Page 20
    In contrast, Plaintiffs allege that they entered a room Defendants filled with a
    cloud of toxic chemicals, and became ill within fifteen minutes of their exposure to the
    toxins. Moreover, the record shows that exterminators acting on behalf of Defendants
    entered the room to exterminate cockroaches, and that at least one pesticide that
    Defendants use to control cockroaches—Demand CS—is capable of producing many of
    the symptoms from which Plaintiffs suffer. It does not take an expert to conclude that,
    under these circumstances, Defendants more likely than not are responsible for
    Plaintiffs’ injuries.
    If anything, the decision in Kalamazoo River bolsters Plaintiffs’ case. Like the
    defendant in Kalamazoo River, who introduced scientific evidence showing that it was
    not responsible for PCB contamination along the shoreline, Plaintiffs have introduced
    scientific evidence—the MSDS—which shows that Demand CS is capable of causing
    their symptoms. See 
    171 F.3d at 1067
    . Defendants, like the plaintiff in Kalamazoo
    River, have introduced no evidence regarding the toxic effects of Demand CS. See 
    id.
    at 1072–73. Defendants cannot excuse their failure to introduce expert testimony by
    accusing their adversaries of the same failure where other scientific evidence exists that
    tends to prove Plaintiffs’ case.
    Should a jury credit Plaintiffs’ testimony, it reasonably could conclude that the
    alleged cloud of unidentified toxic chemicals sprayed in Plaintiffs’ hotel room caused
    Plaintiffs’ injuries. The dissent, however, asserts that Plaintiffs were required to produce
    expert testimony linking their exposure with their symptoms. According to the dissent,
    “ordinary understanding of everyday medical problems does not include the proposition
    that black tongue is ordinarily caused by spraying of pesticides.” Dissenting Op. at 30-
    31. The dissent appears to believe that a jury in Plaintiffs’ case would have to use its
    own knowledge to link pesticide exposure to Plaintiffs’ illness and its symptoms.5
    5
    The dissent asserts that Plaintiffs were required to produce expert testimony to establish
    causation in this case. To support its argument, the dissent cites to an unpublished decision from the
    Michigan Court of Appeals. See Dissenting Op. at 6-7 (citing Trice v. Oakland Dev. Ltd. P’ship, No.
    278392, 
    2008 Mich. App. LEXIS 2484
    , at *32 (Mich. Ct. App. Dec. 16, 2008)). While similar to the facts
    involved in this case, Trice, as the dissent acknowledges, relies primarily on the reasoning of the very
    district court decision which is before this panel on appeal. Further, under Michigan law, an unpublished
    opinion from the state court of appeals lacks precedential value and is not binding on state courts. Mich.
    No. 07-1733            Gass, et al. v. Marriott Hotel Servs., et al.               Page 21
    However, Dr. Natzke stated in his affidavit that, based on his experience in treating
    patients who have been exposed to pesticides, a discolored tongue is attributable to
    pesticide poisoning. Thus, contrary to the dissent’s assertions, our conclusion that
    Plaintiffs were not required to produce expert testimony with respect to causation is not
    a conclusion that the causes of a black tongue are within the “ordinary understanding”
    of the jury.
    We conclude that when a plaintiff claims that a defendant was negligent in filling
    a hotel room with a cloud of a poisonous substance, and there is evidentiary support for
    such claims, expert testimony is not required to show negligence, and the district court
    erred in holding otherwise.
    IV.      PLAINTIFFS’ MOTION TO EXTEND DISCOVERY
    Finally, we note that, at oral argument, Plaintiffs claimed that they would have
    presented more evidence indicating that they were injured by Demand CS or Suspend
    SC, but they were frustrated in their efforts to conduct discovery because Defendants did
    not provide Plaintiffs with documents showing that these two pesticides were used at the
    Maui Marriott until after the close of discovery. Although Plaintiffs filed a motion in
    the district court seeking to extend the length of discovery in light of Defendants’ alleged
    failure to reveal damaging documents in a timely manner, the district court denied this
    motion, and Plaintiffs do not appeal the district court’s ruling. Accordingly, we decline
    to review the district court’s decision not to permit additional discovery. See United
    States v. Corrado, 
    304 F.3d 593
    , 611 n.12 (6th Cir. 2002) (“Arguments not developed
    in briefs on appeal are deemed waived by this court . . . .”). We leave it to the district
    court on remand to determine whether to reopen discovery to expand the record prior to
    trial.
    App. R. 7.215(C)(1).
    No. 07-1733       Gass, et al. v. Marriott Hotel Servs., et al.             Page 22
    CONCLUSION
    Accordingly, for the reasons set forth above, we REVERSE the grant of
    summary judgment to Defendants and REMAND this case to the district court for a jury
    trial.
    No. 07-1733        Gass, et al. v. Marriott Hotel Servs., et al.                  Page 23
    ________________
    DISSENT
    ________________
    BOGGS, Chief Judge, dissenting. This case basically boils down to the relative
    import of two Latin phrases: “post hoc ergo propter hoc” and “res ipsa loquitur.” The
    former is a well known logical fallacy (recognized as such since Aristotle’s Rhetoric).
    It is the fallacy of saying that because effect A happened at some point after alleged
    cause B, the alleged cause was the actual cause. Such logic has never been enough to
    survive summary judgment. See, e.g., Abbott v. Federal Forge, 
    912 F.2d 867
    , 875 (6th
    Cir. 1990) (“[P]ost hoc, ergo propter hoc is not a rule of legal causation.”).
    The latter phrase applies to a narrow class of cases in which the connection
    between an untoward effect and some type of fault is so clear (and the likelihood of an
    alternative explanation so low) that no other evidence is required to uphold a jury
    verdict. The original, and classic, exposition of this principle is Byrne v. Boadle, 159
    Eng. Rep. 299 (Exch. 1863), a nineteenth century English case where a pedestrian on the
    streets of Liverpool was struck by a barrel of flour that came flying out of the second-
    story window of a commercial storeroom. As I will explain below, it seems clear to me
    that the venerable British case does not describe the case before us. A barrel of flour is
    extremely unlikely to come flying out onto a city street without some fault by those
    charged with the care of similar barrels, and it is also extremely unlikely that the flying
    barrel of flour came from any place other than the adjacent flour warehouse.
    In our case, the plaintiffs’ symptoms, which worsened at a later time and after
    medical care, and which are known to have a wide variety of possible causes, are much
    less obviously connected to an unspecified dose of a potentially poisonous pesticide.
    Instead, finding fault, without more, in the latter circumstances represents classic post
    hoc reasoning. Something potentially causative happened at one time; something
    untoward happened at a later time. Therefore, plaintiffs allege, the latter must have been
    caused by the former.       The applicable law of Michigan does not permit that
    unsubstantiated connection to be made, and that is why expert opinion is required. I
    No. 07-1733            Gass, et al. v. Marriott Hotel Servs., et al.               Page 24
    therefore respectfully dissent from the majority’s invocation of res ipsa in a case where
    it is not warranted.
    I
    This case involves assessing the connection between exposure to some chemical
    substance and a series of physical symptoms that are generally attributable to a wide
    variety of causes. The district court held that the experts that the plaintiffs relied on to
    connect the alleged exposure (and the defendant’s behavior relating to it) to the
    plaintiffs’ symptoms could not testify to any causal relationship. The majority affirms
    that decision but nevertheless reverses summary judgment, holding that ordinary
    experience suffices to connect any chemical used (regardless of composition or dose) to
    the symptoms. In my view, this resolution is not supported by common sense or by the
    Michigan law that governs the case. Both counsel that a lay juror cannot be expected
    to understand the complex medical and scientific facts that necessarily underlie any such
    an attribution of fault and, accordingly, require expert explanation prior to allowing a
    jury verdict. The majority’s assessment that in this case (and, one supposes, unlike in
    most toxic tort cases) there is sufficient evidence for the jury to charge plaintiffs’
    illnesses to the defendants because the illness began to develop reasonably soon after the
    exposure – which is only post hoc ergo propter hoc – reinforces rather than refutes this
    preference for expertise.
    To fully understand the weight that the majority asks the post hoc fallacy to bear,
    it is useful to begin with a point of agreement between the majority and this opinion.
    The plaintiffs hoped that their treating physicians could testify not just to the physical
    symptoms with which they were diagnosed but also to the likely cause of such
    symptoms. That testimony would have concluded that the plaintiffs’ illnesses were
    explained best by chemical poisoning and that the exposure to whatever pesticides
    defendants had used was the best explanation of how plaintiffs came in contact with the
    chemicals that poisoned them. As rehearsed and affirmed in the majority opinion, the
    district court held that these doctors lacked sufficient expertise to make the causal
    connection alleged by plaintiffs.
    No. 07-1733           Gass, et al. v. Marriott Hotel Servs., et al.                 Page 25
    Plaintiffs also proffered the testimony of a second set of experts to demonstrate
    duty and breach. These liability experts (whose exclusion was not challenged on appeal)
    would have testified to the dangers of pesticides and an appropriate standard of care for
    their use. The district court excluded them because they prepared no report and did not
    plan to give an opinion about the chemicals that defendants actually used or the
    precautions defendants actually undertook.
    Together, this missing expert testimony means that the summary judgment record
    contains no admissible evidence that directly shows a breach of duty or that shows
    causation between the alleged breach and the illnesses. To be sure, the plaintiffs’
    evidence recounts the spraying of the pesticide and details the potential toxicity at some
    unspecified dose of the chemicals that probably were sprayed by defendants. But
    establishing these propositions does not establish how the room should have been
    sprayed or how the risk of chemical poisoning should have been reduced. That is, the
    evidence does not tend to prove that the defendants’ activities, in light of the relevant
    standard of care, were negligent or that the chemicals that were sprayed caused the
    illness.
    Of course, the absence of evidence is not the same as evidence of absence. The
    majority holds that in the place of the absent evidence there is sufficient circumstantial
    evidence of breach and causation. Specifically, the historical fact that some illness came
    quickly on the heels of exposure speaks for itself and makes up for the otherwise missing
    causal links.
    II
    Thus presented, the question is whether the plaintiffs needed expert testimony
    in this case to prove how much chemical exposure is too much chemical exposure or to
    prove whether the amount of exposure actually caused the alleged harmful consequence.
    In my view, the majority pays too little attention to this issue, rushing from the fact of
    exposure and odd symptoms to the legal conclusion of fault. It is of course correct that
    under Michigan law some complex cases involve breach or causation questions within
    the ken of the jury notwithstanding the professional or scientific nature of the litigation.
    No. 07-1733         Gass, et al. v. Marriott Hotel Servs., et al.                   Page 26
    See Thomas v. McPherson Health Center, 
    400 N.W.2d 629
    , 631 (Mich. Ct. App. 1986).
    But the majority assumes, without citation or authority, that this case is such a case.
    In Michigan, expert testimony in professional negligence (and toxic tort) cases
    like this one is required to avoid summary judgment “unless the lack of professional care
    is so manifest that it would be within the common knowledge and experience of the
    ordinary layman that the conduct was careless . . . .” Lince v. Monson, 
    108 N.W.2d 845
    ,
    848 (Mich. 1961). The Michigan courts do not provide a test for what is common
    knowledge, but do require more than “a bad result,” Jones v. Porretta, 
    405 N.W. 863
    ,
    874 (Mich. 1981), and have frequently held that negligence cannot be inferred based on
    ordinary knowledge simply from an unexpected injury. See, e.g., Woodard v. Custer,
    
    702 N.W. 2d 522
    , 525 (Mich. 2005) (“[W]hether a leg may be fractured in the absence
    of negligence when placing an arterial line . . . in a newborn’s leg is not within the
    common understanding of the jury . . . .”). This approach comports with the general
    view that injuries in professional negligence cases, especially those involving complex
    chemicals and human health, “are usually not immediately obvious and the connection
    between exposure and injury is not a matter of common sense or everyday experience.”
    In re Meridia, 
    328 F. Supp. 2d 791
    , 798 (N.D. Ohio 2004).
    As I understand it, these cases require expert testimony in complex, professional,
    or scientific-based negligence cases in order to limit the dangers associated with
    indulging the post hoc impulse: it is too easy to charge an uncommon harm to the
    presence of a mysterious substance. Properly credentialed expert testimony operates
    as a bulwark against such fallacious attribution of guilt. As in the Daubert context, our
    concern in applying these cases should be to “assure that the powerful engine of tort
    liability . . . points towards the right substances and does not destroy the wrong ones.”
    General Electric v. Joiner, 
    522 U.S. 136
    , 148-49 (1997) (Breyer, J. concurring).
    While our case is not a “professional care” case, in a very recent, albeit
    unpublished, decision, the Michigan Court of Appeals applied this wisdom to a case
    similar to ours. The court, citing favorably to the district court opinion in this case, held
    that without expert testimony directly connecting the level of pesticide exposure to the
    No. 07-1733         Gass, et al. v. Marriott Hotel Servs., et al.                   Page 27
    plaintiff’s mysterious illness, a plaintiff alleging pesticide poisoning could not get to the
    jury. See Trice v. Oakland Development Ltd. Partnership, 
    2008 Mich. App. LEXIS 2484
     at *30 (Mich. Ct. App. Dec. 16, 2008) (citing Gass v. Marriott, 
    501 F. Supp. 2d 1011
    , 1023 (W.D. Mich. 2007)). Specifically, “the dose of chemicals to which plaintiff
    had been exposed had not been determined,” id. at *32, and so “without evidence that
    plaintiff had been exposed to any chemicals at a level that would be harmful, plaintiff
    could not establish specific causation.” Id. at *35.
    It is against this background that I disagree with the majority’s conclusion that
    the plaintiffs’ proof, without expert testimony, survives summary judgment.
    III
    As a general matter, the weakness in the majority’s reasoning is demonstrated
    by reference to the emotive language used to characterize the facts. The words assume
    negligence and, accordingly, make it easy to agree that a lay person could come to an
    informed conclusion about the case. For instance, the cloud of pesticide was “toxic or
    hazardous,” Op. at 16, and it delivered a “high dose,” Op. at 20, of chemical exposure
    because of defendants’ “unacceptable behavior,” Op. at 15. But one cannot know that
    these conclusions (that should be based on scientific facts of how a chemical impacts the
    human body and legal standards) are appropriate without an expert explaining what
    amount constitutes a high dose or how much exposure makes a chemical toxic to the
    human body. Cf. Woodard, 702 N.W.2d at 526-27. It is surely common experience that
    pesticides are poison, but that does not resolve the question at issue in this litigation: it
    may be that being exposed to a room “sort of cloudy” with Demand CS will cause no
    lasting effects if the exposure is five minutes but not ten; ten but not twenty.
    The majority avoids the difficulty of scientific judgments by simply defining the
    exposure as a high dose and the defendants’ behavior as unacceptable. Of course a jury
    can decide for a plaintiff if it is shown that because of a defendant’s action a poisonously
    high dose of a pesticide was administered to the plaintiff. But a closer examination of
    the summary judgment record reveals that the evidence the plaintiffs have adduced does
    not establish anything close to that description of defendants’ behavior and the
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    majority’s holding is premised on a mistaken belief that a lay jury is competent to set the
    standard of care for the administration of pesticides and to determine the cause of a
    mystery illness.
    A
    In reversing the district court’s breach holding, the majority asserts that a
    “factfinder is able to weigh and evaluate the evidence based on his or her ordinary
    experience,” Op. at 15, because the plaintiffs testimony established that the defendants’
    action resulted in a “thick, horrid, acrid, putrid” cloud of pesticides in the room. The
    “because” in the previous sentence, the effect of which is to make it unnecessary for the
    plaintiffs’ to introduce expert testimony establishing a breach of duty, is not supported
    by law.
    As to the danger of the chemicals (and presumably the duty of care), the evidence
    cited by the majority is the following: (1) the substance sprayed left the hotel room “sort
    of cloudy” and (2) the MSDS report for two of the substances possibly used
    demonstrates that exposure may result in certain symptoms. As to the defendants’
    behavior, the majority cites the following evidence: (1) men in masks entered the hotel
    room and sprayed pesticides despite the presence of suitcases and other indicia of
    occupancy and (2) defendants were aware that “some of the chemicals they routinely use
    could cause serious illness . . . .” Op. at 16.
    This is underwhelming proof of defendants’ alleged breach of a duty of care.
    The evidence leaves open more questions than it answers. We do not know how harmful
    the chemicals are or under what circumstances those harms obtain. For instance, how
    long do the symptoms persist? How much exposure triggers what symptoms? What
    measures (besides ventilation) can prevent harm? How many parts per million make a
    room “cloudy”? How much chemical concentration before a “sort of cloudy” room
    becomes dangerous? Similarly, the evidence is silent about defendants’ behavior in
    relation to a standard of care. For instance, which chemical was sprayed? Is a hotel
    room “well ventilated”? Does the chemical effect dissipate? How fast? What is its
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    effect on articles in a room? How long does it last? Must a room be vacant to be
    sprayed?
    As I understand Michigan’s tort law, the gaps in the evidence suggested by these
    questions are too wide to be bridged by jury inference. To be sure, the difference
    between “common knowledge” and a fact that must be explained by expert testimony
    has not been precisely defined. But wherever the line may be, the questions posed in the
    previous paragraph about health effects and proper precautions to mitigate them appear
    to me well beyond the ordinary ken of a juror. See Thomas, 
    400 N.W.2d at 630
    (upholding a directed verdict for the defendant where “[p]laintiffs provided expert
    testimony that [their proffered theories of liability] would constitute a breach of the
    appropriate standard of care” but “they did not produce evidence in the form of expert
    opinion that the health center had in fact breached the standard of care.”).
    The majority makes no attempt to argue to the contrary based on the plaintiffs’
    evidence. They assert only that “[e]xpert testimony is not necessary to establish that
    such egregious behavior does not conform to the standard of care” because “an ordinary
    person understands that it is unacceptable to enter a place where another is residing and
    fill that place with airborne poison, without providing for evacuation of the inhabitants,
    appropriate ventilation, or taking other precautions.” Op. at 15. This assertion fails for
    two reasons.
    First, there is no evidence (lay or expert) to support the majority’s premises about
    what the defendants did. There is no evidence as to which pesticide was used (that is,
    how poisonous the “airborne poison” actually was – on the plaintiffs’ allegations, there
    are differences between Demand CS and Suspend SC); that it would linger long enough
    to seriously harm someone; that complete evacuation of all property in the room was
    necessary; that a modern hotel room is not appropriately ventilated; or that “other
    precautions” were necessary. The assertion thus fails on its own terms.
    Second, it asserts without argument that the standard of care is common
    knowledge. This is unsupportable. Some pesticides can be used in a home by a private
    individual without supervision or extra preparation and some require the tenting and total
    No. 07-1733            Gass, et al. v. Marriott Hotel Servs., et al.                            Page 30
    evacuation of the home. Simply reading the MSDS reports (whose warnings as to
    Suspend SC and Demand CS mirror the warnings on the can of over-the-counter Ant &
    Roach Killer in my chambers1) as the majority does cannot explain the difference. The
    majority may be correct that if the jury knew all that was required of the defendants
    under the appropriate level of care, it could compare the plaintiffs’ version of events to
    that duty and make a breach determination. But that is not the case we have before us.
    In our case an expert is required to explain the potential hazards associated with certain
    pesticides and the best practices for avoiding those hazards.
    B
    The majority’s causation analysis is even less persuasive. It boils down to an
    assertion that there is evidence of causation because the defendants sprayed a pesticide,
    scientific evidence shows that one of the pesticides they may have sprayed causes certain
    physical symptoms, and the plaintiffs did in fact experience those symptoms. The
    missing premises from this argument – that defendants did spray the substance known
    to be dangerous, that the spray was in sufficient amount to cause harm, that plaintiffs’
    minutes-long exposure was sufficient to cause harm, that other causes can be excluded
    with confidence, etc. – are almost too many to list.
    The majority holds that those premises can be supplied by inference. The
    opinion, however, makes no attempt to explain why the causal link between the
    defendants’ actions and the plaintiffs’ illnesses are within common experience. There
    is good reason to think that it is not. For instance, ordinary understanding of everyday
    medical problems does not include the proposition that black tongue is ordinarily caused
    by spraying of pesticides.2 To be sure, an ordinary lay person probably begins with an
    1
    For example, compare the warning the majority cites for the proposition “mere skin contact with
    Demand CS is dangerous” at page 15 of the opinion with the over-the-counter warning regarding contact
    with skin or clothing: “Take off contaminated clothing. Rinse skin immediately . . . for 15-20 minutes.
    Call a poison control center or doctor for treatment advice.”
    2
    Indeed, publically available information suggests many other, more common, causes: (1)
    changes in the normal bacteria or yeast content of the mouth following antibiotic treatment; (2) poor oral
    hygiene; (3) medications containing bismuth, such as Pepto-Bismol; (4) regular use of mouthwash
    containing oxidizing agents; and (5) drinking excessive amounts of coffee or tea. See Alan Carr,
    What Causes a Black Hairy Tongue? Mayo Clinic: Ask a Dental Specialist, available at
    No. 07-1733          Gass, et al. v. Marriott Hotel Servs., et al.                      Page 31
    assumption that black tongue is evidence of something gone wrong, but the question here
    is what that something is and whether it is chargeable to the defendants’ actions. See
    Thomas, 
    400 N.W.2d at 631
     (rejecting an argument similar to plaintiffs’ because the
    “injury was susceptible to a number of explanations, all of which required medical
    knowledge to discern.”).
    The majority’s reliance, at pages 20-21, on Dr. Natzke’s statement that pesticide
    exposure could cause black tongue to show that the jury would possess the knowledge
    necessary to make a reliable attribution of fault is not persuasive. First, Dr. Natzke does
    not say that the plaintiffs’ injuries are the result of pesticides or even that these pesticides
    could cause black tongue. Second, not only is there a lack of knowledge about how the
    condition comes about, reliance on Natzke’s statement would permit lay people to make
    a determination about the cause of an unfamiliar medical condition based only on a post
    hoc temporal connection and an abstract statement of a risk of harm.
    IV
    We need to look no further than this case for an illustration of the concerns
    underlying my belief that these standard of care and causation issues require expert
    explanation. The flaws in the majority’s reasoning – eliding the difficult scientific
    questions; conflating colloquial usage of terms like “toxic” and “high dose” with
    scientific conclusions about the health effects of the plaintiffs’ exposure; and attributing
    causation on the basis of order of events – are the reasons lay people (jurors and judges
    alike) are advised to take expert guidance in drawing scientific conclusions. I believe
    our courts should require that guidance. I respectfully dissent.
    http://www.mayoclinic.com/health/black-hairy-tongue/HQ00325. Similarly, an OSHA document included
    by plaintiffs in the summary judgment record that describes their diagnosis of “Multiple Chemical
    Sensitivities” admits that “[t]here is insufficient scientific evidence to confirm a relationship
    between . . . possible causes and symptoms.” J.A. 564.