Roskop Dairy v. GEA Farm Tech. ( 2015 )


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  •                                     - 148 -
    Nebraska A dvance Sheets
    292 Nebraska R eports
    ROSKOP DAIRY v. GEA FARM TECH.
    Cite as 
    292 Neb. 148
    Roskop Dairy, L.L.C., appellant, v. GEA
    Farm Technologies, Inc., and Midwest
    Livestock Systems, Inc., appellees.
    ___ N.W.2d ___
    Filed December 4, 2015.   No. S-14-115.
    1.	 Trial: Expert Witnesses: Appeal and Error. An appellate court reviews
    de novo whether the trial court applied the correct legal standards for
    admitting an expert’s testimony.
    2.	 ____: ____: ____. An appellate court reviews for abuse of discretion
    how the trial court applied the appropriate standards in deciding whether
    to admit or exclude an expert’s testimony.
    3.	 Summary Judgment: Appeal and Error. In reviewing a summary
    judgment, an appellate court views the evidence in the light most
    favorable to the party against whom the judgment was granted and
    gives that party the benefit of all reasonable inferences deducible from
    the evidence.
    4.	 Evidence: Appeal and Error. Generally, the control of discovery is a
    matter for judicial discretion, and decisions regarding discovery will be
    upheld on appeal in the absence of an abuse of discretion.
    5.	 Prejudgment Interest: Appeal and Error. Prejudgment interest may
    be awarded only as provided in Neb. Rev. Stat. § 45-103.02 (Reissue
    2010), and whether prejudgment interest should be awarded is reviewed
    de novo on appeal.
    6.	 Summary Judgment. A motion for summary judgment shall be granted
    where there is no genuine issue as to any material fact and the moving
    party is entitled to judgment as a matter of law.
    7.	 Evidence: Proof. Failure of proof concerning an essential element of the
    nonmoving party’s case necessarily renders all other facts immaterial.
    8.	 Summary Judgment: Proof. A party moving for summary judgment
    makes a prima facie case for summary judgment by producing enough
    evidence to demonstrate that the movant is entitled to judgment if the
    evidence were uncontroverted at trial.
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    Nebraska A dvance Sheets
    292 Nebraska R eports
    ROSKOP DAIRY v. GEA FARM TECH.
    Cite as 
    292 Neb. 148
    9.	 ____: ____. Once the moving party makes a prima facie case, the bur-
    den shifts to the party opposing the motion to produce admissible con-
    tradictory evidence showing the existence of a material issue of fact that
    prevents judgment as a matter of law.
    10.	 Summary Judgment: Evidence. Conclusions based on guess, specula-
    tion, conjecture, or a choice of possibilities do not create material issues
    of fact for the purposes of summary judgment; the evidence must be
    sufficient to support an inference in the nonmovant’s favor without the
    fact finder engaging in guesswork.
    11.	 Products Liability: Warranty. All implied warranty theories of recov-
    ery and strict liability claims for manufacturing defect, design defect, or
    failure to warn seek to recover for a “defect.”
    12.	 Actions: Negligence: Warranty: Proximate Cause. Whether a plaintiff
    is proceeding under negligence, defect theories, or breach of express
    warranty, proximate cause is a necessary element of the plaintiff’s case.
    13.	 Negligence: Proximate Cause: Words and Phrases. Proximate cause
    is the cause that in a natural and continuous sequence unbroken by an
    efficient intervening cause, produces the injury, and without which the
    injury would not have occurred.
    14.	 Negligence: Proximate Cause: Proof. To establish proximate cause, the
    plaintiff must meet three basic requirements: (1) Without the negligent
    action, the injury would not have occurred, commonly known as the
    “but for” rule or “cause in fact”; (2) the injury was a natural and prob-
    able result of the negligence; and (3) there was no efficient interven-
    ing cause.
    15.	 Expert Witnesses: Testimony. Findings of fact as to technical matters
    beyond the scope of ordinary experience are usually not warranted in the
    absence of expert testimony supporting such findings.
    16.	 Testimony. It is well settled that a causation opinion based solely on a
    temporal relationship is not derived from the scientific method and is
    therefore unreliable.
    17.	 Products Liability: Proof. Under the malfunction theory, also some-
    times called the indeterminate defect theory or general defect theory, a
    plaintiff may prove a product defect circumstantially, without proof of
    a specific defect, when (1) the incident causing the harm was of a kind
    that would ordinarily occur only as a result of a product defect and (2)
    the incident was not, in the particular case, solely the result of causes
    other than a product defect existing at the time of sale or distribution.
    18.	 Circumstantial Evidence: Verdicts. Circumstantial evidence is not
    sufficient to sustain a verdict that depends solely thereon unless the cir-
    cumstances proved by the evidence are of such a nature and so related
    to each other that the conclusion reached by the jury is the only one that
    can fairly and reasonably be drawn therefrom.
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    Nebraska A dvance Sheets
    292 Nebraska R eports
    ROSKOP DAIRY v. GEA FARM TECH.
    Cite as 
    292 Neb. 148
    19.	 Juries: Evidence. Where, under the facts viewed in a light most favor-
    able to the nonmoving party, the nonexistence of the fact to be inferred
    is just as probable as its existence, the conclusion that it exists is a
    matter of speculation, surmise, and conjecture, and a jury will not be
    permitted to draw it.
    20.	 Evidence. The line between impermissible speculation and reasonable
    inferences is drawn by the laws of logic.
    21.	 ____. Reasoning causation from temporal correlation represents a logi-
    cal fallacy. A conclusion based upon such reasoning is not a reasonable
    inference but is mere speculation and conjecture.
    22.	 Rules of the Supreme Court: Appeal and Error. It is incumbent
    upon the party appealing to present a record which supports the errors
    assigned. Neb. Rev. Stat. § 25-1140 (Reissue 2008) and Neb. Ct. R.
    App. P. § 2-105(B)(1)(b) (rev. 2010) place the burden on the appel-
    lant to file a praecipe identifying the matter to be contained in the bill
    of exceptions.
    23.	 Prejudgment Interest: Claims. A claim is liquidated for purposes of
    prejudgment interest when there is no reasonable controversy as to both
    the amount due and the plaintiff’s right to recover.
    Appeal from the District Court for Gage County: Paul W.
    Korslund, Judge. Affirmed in part, and in part reversed.
    Kristopher J. Covi, of McGrath, North, Mullin & Kratz,
    P.C., L.L.O., for appellant.
    Stephen L. Ahl and Nathan D. Anderson, of Wolfe, Snowden,
    Hurd, Luers & Ahl, L.L.P., for appellee Midwest Livestock
    Systems, Inc.
    William M. Bremer and Ann M. Byrne, of Bremer & Nelson,
    L.L.P., and Catherine L. Stegman and Joseph S. Daly, of
    Sorodo, Daly, Shomaker & Selde, P.C., L.L.O., for appellee
    GEA Farm Technologies, Inc.
    Connolly, Stephan, McCormack, Miller-Lerman, and
    Cassel, JJ.
    McCormack, J.
    NATURE OF CASE
    A dairy appeals from the district court’s order of summary
    judgment in favor of a manufacturer of a microprocessor-based
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    ROSKOP DAIRY v. GEA FARM TECH.
    Cite as 
    292 Neb. 148
    milking control unit and the dealer of that unit (collectively the
    defendants). The principal issue is whether the dairy rebutted
    the defendants’ prima facie case that mechanical components
    of the milking system maintained by the dairy and not a part
    of the microprocessor-based control unit were the proximate
    cause of the alleged damages.
    BACKGROUND
    Roskop Dairy, L.L.C. (Roskop Dairy), owned by Michael
    Roskop (Roskop), is a commercial dairy operation. GEA Farm
    Technologies, Inc. (GEA), manufactures automated dairy
    equipment used in dairy systems. Midwest Livestock Systems,
    Inc. (Midwest), was an authorized dealer of GEA products.
    Roskop Dairy sued the defendants for damages allegedly
    stemming from the “Dematron 60 Air Detacher Package”
    (Dematron) manufactured by GEA and purchased by Roskop
    Dairy from Midwest. The total purchase price was $153,027.88.
    Roskop Dairy paid Midwest a downpayment of $33,600 and
    made a second payment of $70,000. Roskop Dairy never paid
    the remainder.
    The installation of the Dematron at Roskop Dairy occurred
    in June 2008. There was no evidence of a service agreement
    by which Midwest was to regularly inspect or maintain other
    component parts of Roskop Dairy’s milking system that were
    not provided by Midwest.
    Roskop Dairy sued the defendants for breach of express and
    implied warranties and negligence. Roskop Dairy theorized
    that Midwest negligently and defectively installed and pro-
    grammed the Dematron. Specifically, Roskop Dairy asserted
    that improper parameter settings caused the milking units to
    detach while still under significant vacuum and thereby harmed
    the teats of the dairy cows, resulting in mastitis and lowered
    milk production. Roskop Dairy did not allege liability based on
    negligent maintenance of the physical component parts of the
    milking system that are not part of the Dematron.
    The defendants generally denied liability and asserted that
    Roskop Dairy’s contributory negligence barred any claim
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    ROSKOP DAIRY v. GEA FARM TECH.
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    against them. Midwest counterclaimed for the principal amount
    still due under the sales contract agreement, as well as for 8
    percent interest per annum from the payment due date. After
    discovery, the defendants moved for summary judgment.
    Milking System, Dematron,
    and Somatic Cell Counts
    Roskop Dairy has 50 milking “parlors” used to milk approx-
    imately 700 cows. When a cow enters a parlor, an employee of
    Roskop Dairy manually prepares the cow’s teats by cleaning
    them and stimulating let down. The employee then presses a
    button to apply vacuum to the milking “claw.” The employee
    applies the claw to the teats, and milking begins. Milk flows
    through tubes into holding tanks. The claw, vacuum, tubes, and
    tanks are not part of the Dematron.
    The Dematron is a microprocessor-based milking control
    unit that monitors signals from milking sensors in the milk-
    ing system and sends signals to that system to control when
    various processes take place after manual application of the
    claw. There are multiple parameter settings involved in the
    functioning of the Dematron. These settings are preset at the
    factory, but are regularly adjusted to accommodate dairy own-
    ers’ preferences.
    The “milk flow threshold” level is an adjustable Dematron
    parameter that indicates when the system should finish milk-
    ing. Another Dematron parameter, “blink time,” is the length
    of time a cow must be below the milk flow threshold before
    detachment of the claw will start. A component in the sys-
    tem actually blinks during the blink time, and milk flow can
    also be observed through clear lenses attached to the top of
    the claw. After the cow is below the milk flow threshold for
    the desired blink time, the Dematron shuts off the vacuum
    by sending a signal to a “shifting valve” that is also part of
    the Dematron.
    After the vacuum is shut off, it should quickly dissipate.
    Depending on the model of claw, vacuum dissipates either
    through vents in the metal claw itself or in clear plastic
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    ROSKOP DAIRY v. GEA FARM TECH.
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    replaceable lenses that attach to the top of the claws. In the
    model of claw used at Roskop Dairy, the vents were located in
    the lenses and not in the claw itself.
    The “detach delay” is a setting of the Dematron that controls
    the time between when the vacuum is shut off and the claw is
    retracted by the automated system. Retraction ideally occurs
    when most, but not completely all, of the residual vacuum has
    dissipated through the vents. If no residual vacuum is left when
    the claw retracts, the claw will fall, rather than be retracted,
    and will land on the parlor deck.
    The “milk sweep delay” is a Dematron setting controlling
    the time between when the claw is retracted and when the
    “milk sweep begins.” The “milk sweep” is an optional setting
    and consists of a short burst of vacuum to pull any residual
    milk into the tubes of the milking system.
    After detachment, the cows’ udders are manually dried with
    a cloth by Roskop Dairy employees.
    The somatic cell count of the milk at a dairy is an indica-
    tor of the number of mastitis organisms in the herd. Increased
    somatic cell count can mean either many cows with a lesser
    degree of infection or fewer cows with a worse infection.
    Somatic cell counts above 400,000 are “concerning.” Below
    200,000 represents a well-managed herd.
    While the somatic cell count in Roskop Dairy’s herd had
    previously been in the 200,000 range, in January 2008, before
    the installation of the Dematron, it significantly increased to
    409,000, from 285,000 the previous month. The somatic cell
    count continued in the 409,000 to 476,000 range until June
    2008, when it reached 510,000.
    In July 2008, after installation of the Dematron, the somatic
    cell count rose to 627,000. It went back down to 493,000 in
    August, after Dematron employees visited Roskop Dairy. It is
    undisputed that during that visit, Dematron employees adjusted
    some parameter settings of the Dematron.
    Roskop Dairy claims that the rise in somatic cell counts in
    the herd after installation of the Dematron corresponded to
    a reduction in milk production that had not occurred during
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    ROSKOP DAIRY v. GEA FARM TECH.
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    the pre-Dematron rise in somatic cell counts. Roskop did not
    address the extent to which any changes in milking practices
    entered into this conclusion. Roskop had milked his cows
    three times a day until July 2, 2008. Since July 2, however,
    he has milked his cows twice a day. Milking three times a
    day versus twice a day would increase milk yield by 12 to
    15 percent.
    Deposition of Michael Roskop and
    K aren Cass’ M astitis R eports
    Roskop’s deposition was entered into evidence at the sum-
    mary judgment hearing. Roskop testified that due to the timing
    of events, he believed the July 2008 increase in the somatic
    cell count was caused by the parameters of the Dematron’s
    being set incorrectly the previous month. Roskop admitted that
    he was not an expert on milking machines. He admittedly did
    not fully understand the Dematron settings. But he stated that
    approximately 20 days after the system was installed, his herd
    experienced an increase in mastitis.
    Roskop suspected, first, that from the time the system was
    installed until July 31, 2008, when Midwest employees made
    further adjustments to the Dematron’s parameter settings, the
    blink time was set too short, such that the machines were
    detaching before the cows were fully milked. He believed this
    based on the appearance of the cow udders and the fact that the
    cows were not producing as much milk as he expected.
    Roskop admitted the blink time setting did not lead to mas-
    titis, however. Roskop testified that his employees manually
    reattached the system when the cows’ udders appeared to not
    be completely milked out. Roskop did not specifically recall
    which of the original blink time settings and adjustments may
    have been made at his request.
    Roskop suspected that incorrect parameters for the sweep
    time led to the increase in mastitis. Roskop believed that
    from the time of installation until adjustments were made
    on July 31, 2008, incorrect sweep time settings resulted in
    the machine’s detaching while still under a vacuum. This, in
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    turn, tugged on the cows’ teats, causing physical injury that
    made them more susceptible to mastitis. Since discovery,
    Roskop Dairy no longer asserts that the sweep time settings
    led to mastitis.
    Roskop testified that from late June 2008 when the system
    was installed until Midwest employees made adjustments to
    the parameter settings in late July, he witnessed the claw units
    being “jerked off” the cows with a lot of “tugging.” He testi-
    fied that the units were coming off under vacuum and that
    vacuum lasted for approximately 3 seconds before it dissipated.
    Roskop did not clearly explain whether he could determine
    that this vacuum was active vacuum versus residual vacuum.
    At one point, he affirmed that he could hear the hissing of air
    being sucked into the machine for about 3 seconds, but that at
    another point, he affirmed this was the failure of the vacuum to
    dissipate for approximately 3 seconds.
    During the time period that the units were detaching under
    vacuum, Roskop observed approximately one-third of his
    dairy cows with “everted” teat ends. Roskop explained that
    normally only about 2 percent of his cows demonstrated
    everted teat ends. Roskop further observed bruised teats dur-
    ing that time.
    Roskop testified that he had concluded the Dematron was
    in some manner the cause of the detachment under vacuum
    because “when they made the change off of the sweep time,
    that’s when we had the instant change of no more damage to
    the teat end on the cows.” Roskop explained that although the
    cows with damaged teat ends took some time to heal, new
    cases of teat-end damage significantly decreased after Midwest
    employees changed the parameter settings of the Dematron in
    late July.
    Roskop confirmed that Roskop Dairy employees were sup-
    posed to check the lenses of the claws constantly to make sure
    the vents, through which the residual vacuum escapes, were
    not clogged. The most common cause of vent clogging was
    manure. His employees were supposed to unclog the vents if
    they observed them clogged. Roskop did not specify to what
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    292 Neb. 148
    extent his employees were successfully carrying out these
    duties in the summer of 2008. Roskop indicated that sometime
    in June 2008, four Roskop Dairy employees quit, because cows
    were kicking them. Roskop testified that it took approximately
    2 months to replace those employees.
    Roskop testified that he hired Karen Cass, a mastitis con-
    sultant, to “come in and give me an outside look and test the
    herd.” She observed the dairy and tested the cows on July 19,
    2008. Roskop admitted that Cass observed several behaviors
    of Roskop Dairy’s employees that were concerning from the
    standpoint of mastitis prevention. Roskop acknowledged that
    Cass’ report found various deficiencies in his employees’ care
    of the cows during the milking process. Roskop did not deny
    the veracity of Cass’ observations, but hoped those deficiencies
    were isolated instances.
    Cass found there were too many cows with clinical mastitis
    in line being milked with nonclinical cows. Cass found that
    the milk and air tubes were falling off the equipment. Cass
    also saw employees “flipping towels,” meaning that they were
    using the same towel to wipe off the teats of more than one
    cow, and were using towels that were still damp. Cass observed
    that employees were not wearing gloves during manual clean-
    ing and stimulation before attaching the claw. Cass wrote that
    the herd’s teat-end condition “look[ed] good.”
    Roskop blamed the incidents of cows in the line show-
    ing clinical mastitis on the fact that the number of sick cows
    exceeded the capacity of his hospital pen. Roskop believed that
    the backflush system between each cow, in any case, prevented
    cross-contamination.
    Depositions of Dennis Nissen, Gerald Farrier,
    and Jeff Hunt Concerning I nstallation
    and A djustments to Dematron
    Dennis Nissen and Gerald Farrier are Midwest employ-
    ees who install and maintain equipment sold by Midwest,
    including the Dematron. Nissen was the employee who pri-
    marily installed the Dematron at Roskop Dairy, and Farrier
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    occasionally assisted. Their depositions were entered into evi-
    dence at the summary judgment hearing. Jeff Hunt, a GEA
    technical specialist who the parties do not dispute qualifies
    as an expert, was also deposed on two occasions, and his
    depositions were entered into evidence at the summary judg-
    ment hearing.
    Nissen explained that it is normal to adjust the parameter
    settings for the blink time and low milk threshold according
    to the dairy owner’s preferences as to how thoroughly the
    cows are milked. Although Nissen believed that the factory
    settings were correct given his observation of the milk flow
    when he installed the Dematron at Roskop Dairy, he testified
    that he acceded to Roskop’s request to have the cows milked
    more thoroughly by adjusting the parameters of the blink
    time and low milk threshold accordingly. Nissen testified that
    before doing so, he told Roskop that these were not well-
    advised changes and that the cows just needed to get used to
    the new detacher.
    Nissen made followup visits on July 30 and 31, 2008, after
    Roskop had complained of an increase in mastitis. At those
    times, Nissen checked the vacuum settings and observed the
    detachers coming off the cows after milking. He testified that
    he found no problems with the Dematron. Nissen testified that
    he made some “minute” parameter changes.
    Three out of the 50 milking units had plungers that were not
    seating properly, and they were fixed promptly. Hunt testified
    that plungers do not create enough vacuum to cause the kind
    of problems reported by Roskop.
    Nissen and Farrier testified that during their visits in late
    July 2008, they found numerous claws that either did not have
    vented lenses in them or were placed with the vent upside
    down. Of the 50 claws at Roskop Dairy, Nissen found that
    half had to have the lenses replaced. Farrier assumed that
    Roskop or his employees had improperly replaced the lenses.
    Nissen explained that the dairy must be aware of what kind of
    claws it has when ordering replacement lenses, because other
    models of claws do not require vented lenses. Apparently,
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    the vented lenses and unvented lenses are indistinguishable
    besides the presence or absence of a vent.
    Nissen explained that lenses were not part of the detacher
    system sold by Midwest, but were preexisting components that
    mount to the claws. Hunt likewise testified that there is no
    part of the claw system that is part of the Dematron package.
    According to Nissen, Midwest was not charged with maintain-
    ing the claws or the lenses. Most dairy owners, according to
    Nissen, handle their own maintenance of the lenses. Farrier
    similarly explained that it was not “cost conducive” for dairy
    owners to have Midwest maintain their lenses. Although they
    did not consider it to be part of a maintenance obligation,
    Nissen and Farrier used the vented lenses that Roskop had
    on hand and replaced the lenses during their visits in late
    July 2008.
    Hunt visited Roskop Dairy in September 2008. He made
    some “routine adjustments” to a portion of the database kept
    for the parlors, but he did not make any changes affecting the
    detachers. He did not observe anything out of the ordinary in
    the operation of the detacher system.
    Hunt testified that the factory setting for detach delay is 0
    seconds. He explained that the reason for that setting is that
    vacuum detachment cylinders typically do not operate instan-
    taneously. And if the detach delay is set for longer than 0
    seconds, the claw will usually drop before the rope is taut and
    allow the claw to fall to the deck. But detach delay, like other
    settings, may be adjusted by dairy personnel and the installer
    at the time of installation or first use.
    Hunt testified that based on computer records of the
    Dematron settings at the time of installation, the detach delay
    was originally set for 3 seconds around the time of installation.
    When Nissen and Farrier visited Roskop Dairy in late July
    2008, they changed the detach delay setting from 3 seconds to
    10 seconds. By February 2013, however, the detach delay set-
    ting had been reduced from 10 seconds to 1 second.
    Hunt explained that, generally, “[l]enses without vent holes
    or claws with no venting is a cause of poor residual vacuum
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    decay.” Likewise, Nissen and Farrier testified that improper
    venting will cause the claws to detach while still under vac-
    uum. Without proper venting, these witnesses explained, there
    is no way to quickly release the residual vacuum when the
    vacuum is signaled by the Dematron to be turned off.
    Hunt testified that “one of the most prominent and most
    probable” reasons for residual vacuum during retraction of the
    claw is vents not functioning properly. Other physical compo-
    nents of the milking system, however, can also cause residual
    vacuum not to dissipate, such as short air tubes or vacuum
    pulsation. Those other physical components are likewise not
    matters controlled by the Dematron settings or maintained by
    the defendants.
    Having reviewed the records, reports, and Nissen’s depo-
    sition, and taking into account other possible causes, Hunt
    opined that the most likely cause for the claws to retract under
    vacuum in the summer of 2008 was the condition described by
    Nissen of the vents in the lenses of the claws.
    Limited Exclusion of William
    Wailes’ Testimony
    Roskop Dairy had designated William Wailes as an expert
    witness. Wailes has a bachelor’s degree in animal science and
    is a member of the National Mastitis Council. He considers
    himself an expert in management systems, including treatment
    protocols, in the overall operation of a dairy farm. Wailes testi-
    fied that he was not an expert in milking machine equipment
    and that he is not a veterinarian.
    Wailes explained that there are two forms of mastitis.
    Environmental mastitis comes from organisms that are in the
    cow’s environment and typically involve issues of cleanliness,
    keeping the manure under control, changing the bedding, and
    other sanitary conditions. Contagious mastitis does not grow
    in the environment but is passed from cow to cow depend-
    ing on a number of factors. Usually, contagious mastitis is
    passed from infected cows to uninfected cows during milk-
    ing time. Wailes confirmed that according to Cass’ report,
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    both environmental and contagious mastitis was present in
    Roskop’s herd in the summer of 2008. Most of the cases were
    contagious mastitis.
    Wailes testified generally that there are many reasons why
    a dairy herd might have an outbreak of mastitis, which have
    nothing to do with the milking machine. For instance, using
    bare hands rather than gloves when preparing cows for the
    milking machine can increase the spread of mastitis. Using
    damp cloths in the milking parlor is also not advisable, because
    there are opportunities for more colonies of bacteria within the
    damp cloth. Using the same towel for two different cows by
    flipping it over was “unacceptable,” “[b]ecause you can cross-
    contaminate two cows if you use a single towel on two differ-
    ent cows.”
    Further, Wailes testified that milking clinical cows in the
    same line as nonclinical cows can lead to the spread of mas-
    titis. Wailes testified that a backflush system will help pre-
    vent certain types of contagious mastitis from spreading when
    clinical cows are in the line with nonclinical cows, but not
    all. Buying infected cows from other herds could also cause
    an outbreak.
    Wailes had reviewed Cass’ reports in which Cass stated that
    in July 2008, she had observed Roskop’s employees failing to
    use gloves and using damp towels, which they flipped for use
    on multiple cows. Wailes was also aware of Cass’ observation
    that cows with clinical mastitis were being milked with cows
    who did not have mastitis and that other cows with mastitis
    were being kept in sick pens with other cows that did not have
    mastitis. Wailes acknowledged these were “unacceptable” prac-
    tices that could cause the spread of contagious mastitis. Wailes
    did not specifically address the causal role of these practices in
    the rise of mastitis in the Roskop Dairy herd.
    Wailes explained that, physically, the “first and second lines
    of defense” against mastitis are a healthy teat end, “from a
    sphincter muscle skin condition,” and the keratin that is in
    the teat canal. But Wailes did not otherwise elaborate on how
    much more susceptible to contagious mastitis a cow with
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    damaged teat ends might be. Wailes did not testify that teat-end
    damage alone can cause mastitis.
    Wailes further explained that teat-end lesions are “pretty
    rare” and, in normal circumstances, would only result from
    teats being stepped on or similar injuries. Wailes testified that
    vacuum not properly shutting off before retraction of the claw
    could lead to teat-end damage. In addition, certain practices
    leading to overmilking, such as prepping the cow too long
    before milking or a low flow rate setting, could “possibly” lead
    to teat-end damage.
    Although Cass purportedly checked teat health and found
    little evidence of teat-end damage in the herd in July 2008,
    Wailes relied on Roskop’s statement that 30 percent of the
    cows had visible teat-end damage, which would be approxi-
    mately 200 cows. Wailes considered Cass to be qualified to
    evaluate teat-end health—more so than Roskop—and she was
    “[v]ery diligent” in her work. But Wailes questioned the logis-
    tics of Cass’ making such observations while carrying out her
    primary duty of obtaining clean samples from the cows to test
    for mastitis.
    Wailes testified that he did not have the factual informa-
    tion he needed to make a report or a “differential diagnosis
    as to the causes of the cows having mastitis at the Roskop
    Dairy farm in 2008.” Wailes had not reviewed Nissen’s depo-
    sition and had no knowledge of the allegedly clogged vents.
    Neither did Wailes consider, in reaching his opinion, the
    rise in somatic cell count from January to June 2008, before
    installation of the Dematron. Wailes specifically stated that
    he had not ruled out the various other possible causes of a
    mastitis outbreak at Roskop Dairy that would be unrelated to
    the Dematron, because he did not have the necessary records
    to do so.
    Wailes did not know how long the milking system was
    coming off under vacuum. Wailes did not know how many
    units in the system were coming off under vacuum. Wailes
    had no specific information about the hygienic practices at the
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    dairy in the summer of 2008 other than Cass’ report and his
    longtime relationship with Roskop Dairy.
    Wailes stated that he had generally found throughout the
    years that Roskop Dairy was well maintained. When asked
    whether through his discussions with Roskop he had learned
    of any changes in the sanitation practices at Roskop Dairy
    from May to June 2008, Wailes responded, “I think he had
    protocols in place for his milking facility, his people, and so
    that’s, that’s my answer, he had protocols in place.” Wailes
    testified that he did not specifically review what the proto-
    cols were. Wailes further testified that he was not specifically
    aware of what steps were taken at Roskop Dairy to enforce
    its protocols.
    Wailes summarized, “[M]y analysis is that there had to be
    some event to trigger somatic cell counts to take that much of
    a spike.” Citing as the factual foundation for his opinion the
    documentation of a spike in the somatic cell count and his con-
    versation with Roskop in which Roskop related observing the
    units coming off under vacuum and the teat-end damage during
    the time of that spike, Wailes concluded that the alleged dam-
    age to Roskop’s herd was “consistent with” the units detaching
    under vacuum.
    Wailes stated that he did not have the facts to say that units
    coming off under vacuum was the “probable” cause of the
    spike in mastitis. He elaborated that, based on the facts he
    had, he could only say it was “possible” that detachment under
    vacuum caused the spike in mastitis:
    A. It’s very possible, but my, my only backup to that
    would be that when we see a spike in somatic cell counts
    something is causing the mastitis.
    Q. And we’ve agreed it could be many things?
    A. Yes.
    Q. One of which could be something wrong with the
    detacher if indeed there was?
    A. Yes.
    Q. But a lot of other things that have nothing to do
    with the detacher?
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    A. Yes.
    Q. And we can’t rule anyone in or rule anyone out
    based on the facts we have right now?
    A. It’s a dynamic issue.
    But later, Wailes mentioned that “when you try to eliminate
    events that could occur during that period of time, the one that
    you can’t eliminate is the installation of new equipment that
    was not working properly at the time.” Wailes further stated
    at counsel’s prompting that he did not find any other cause
    for the spike in mastitis and loss of production in the summer
    of 2008.
    On this point, Wailes elaborated only that there was no
    change in feed, that Roskop had “protocols in place,” that
    Cass’ report did not necessarily mean that none of the dairy
    workers were exercising good hygiene practices, and that
    he had no reason to believe new cows had been introduced
    into the herd. Wailes then answered affirmatively to Roskop
    Dairy’s counsel’s question as to whether his “analysis that
    the detacher system caused the damage [was] based in part
    on the fact that [Wailes had] either eliminated or not been
    provided with any evidence of any other causes during that
    time frame.”
    But when Midwest’s counsel asked, “You said you didn’t
    find any other cause other than the installation, but fair to
    say you didn’t really look for any other cause other than the
    installation; is that correct?” Wailes answered, “My main con-
    cern at the time was the timing of the events, and the timing
    of the events match up to the installation.” Midwest’s counsel
    then pressed, “But, sir, the question I asked you was did you
    look for any other causes?” Wailes answered, “No.”
    Wailes again clarified that he did not know what, if any-
    thing, was wrong with the Dematron and had no opinion about
    the parameter settings. Wailes stated that he was not an expert
    in the design, installation, diagnosis, settings, or repair of milk-
    ing machine equipment.
    Wailes confirmed generally that “a properly operat-
    ing detacher system” does not “come off under pressure as
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    described by . . . Roskop.” But Wailes also acknowledged
    that there were many reasons other than the Dematron why
    units could come off under vacuum. Wailes described these
    as including improper venting of the claws, misapplication
    of the unit to the udders, kinks in the hoses, and cow move-
    ment. Wailes further conceded there were other parts of the
    milking system that, if not properly maintained by the dairy
    farmer, could cause conditions conducive to cows’ getting con-
    tagious forms of mastitis. Thus, Wailes agreed that it would not
    be “scientific reasoning” to conclude that the Dematron was
    responsible for the claws’ detaching under vacuum.
    The defendants moved to strike Wailes’ testimony on the
    issue of causation, asserting that his testimony represented
    mere speculation and conjecture and was based on unscientific
    methodology and insufficient facts to meet the requirements
    of Schafersman v. Agland Coop.1 The district court granted
    the motion and excluded Wailes’ testimony insofar as Wailes
    sought to opine that the units were coming off under vacuum
    because of something wrong with the Dematron or that the
    increase in mastitis was caused by the units detaching under
    vacuum. Wailes’ deposition was not offered at the summary
    judgment hearing.
    Limited Exclusion of Michael
    Slattery’s Testimony
    Michael Slattery is Roskop Dairy’s veterinarian. In his
    deposition, Slattery discussed in the abstract several possible
    causes of an increased somatic cell count in a dairy herd. In
    addition to the factors discussed by Wailes and acknowledged
    by Roskop in his discussion of Cass’ report, Slattery testi-
    fied that the “inflations” components of the milking machine
    could be worn out and porous, therefore harboring bacteria
    and leading to an increase in mastitis. He also added that
    high temperatures and humidity can lead to an increase in
    1
    Schafersman v. Agland Coop, 
    268 Neb. 138
    , 
    681 N.W.2d 47
    (2004).
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    the spread of mastitis. Finally, milking cows on manual for
    too long could lead to overmilking and increased incidents
    of mastitis.
    Slattery stated he believed that the increase in mastitis at
    Roskop Dairy was due to the Dematron, although he did not
    observe anything wrong with the Dematron and explained that
    he was not an expert on milking machines. Rather, he testified
    that he based his conclusion solely on Roskop’s statement that
    the somatic cell count of the herd increased after the Dematron
    was installed. Slattery conceded he did not look at any data
    and did not eliminate the other possible causes of increased
    somatic cell count that had been discussed.
    Upon the defendants’ motion in limine, the court excluded
    Slattery’s testimony to the extent that it concerned the proxi-
    mate causation of the increased somatic cell count at Roskop
    Dairy in the summer of 2008. Slattery’s deposition was
    offered by Roskop at the summary judgment hearing. It was
    allowed into evidence only to the extent that it contained “fac-
    tual observations.”
    Order Granting Summary Judgment
    The court granted the defendants’ motions for summary
    judgment. In its order, the court noted that it had stricken the
    causation testimony of both Slattery and Wailes as unreliable.
    But it also noted in its order that “[b]oth Slattery and Wailes
    admitted there are numerous possible causes for spikes in a
    dairy herd’s mastitis rate that could not be ruled out in this
    case.” The court noted that there was evidence that Roskop
    Dairy was not following proper hygiene procedures to prevent
    the spread of mastitis. Indeed, the court noted, the somatic
    cell counts indicated a mastitis problem before the Dematron
    was installed.
    The court further noted that Midwest’s expert, Patrick
    Gorden, testified that there was no scientific basis to con-
    clude that the detacher system caused mastitis or decreased
    milk production. Rather, Gorden testified that the mastitis was
    preexisting and likely exacerbated by hot weather and Roskop
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    Dairy’s failure to implement a milk quality program and to
    properly maintain the milking system. Gorden’s affidavit is
    not in the record and apparently was not entered into evidence
    at the summary judgment hearing.
    Finally, the court noted that Hunt opined that Roskop Dairy’s
    failure to properly maintain the vents caused the mastitis. The
    court noted that Roskop had failed to present any expert to
    contradict Hunt’s expert opinion.
    The court reasoned that the fact the detacher units came
    off under vacuum did not in itself demonstrate a product
    defect. Although parameter settings were changed throughout
    the installation process, there was no evidence that any settings
    were incorrect or defective. While, under Genetti v. Caterpillar,
    Inc.,2 proof that a warranted product is defective may be
    circumstantial and inferred from the evidence, the court con-
    cluded that Genetti was inapplicable. There were various pos-
    sible causes of the increase in the somatic cell count or for the
    units detaching under vacuum, which were beyond the normal
    experience and understanding of the jury.
    The court concluded that expert testimony was required for
    a jury to determine which component parts or settings of the
    milking system caused it to come off under vacuum. Expert
    testimony was also required for the jury to determine which,
    among a number of possible causes of the spike in mastitis
    in the herd, was more probable. Roskop Dairy had no such
    expert testimony.
    Prejudgment Interest
    The court subsequently granted summary judgment in favor
    of Midwest on its counterclaim for the remaining principal
    due of $78,026.56 plus prejudgment interest. Because the con-
    tract did not provide for interest, the court applied Neb. Rev.
    Stat. § 45-104 (Reissue 2010):
    Unless otherwise agreed, interest shall be allowed
    at the rate of twelve percent per annum on money due
    2
    Genetti v. Caterpillar, Inc., 
    261 Neb. 98
    , 
    621 N.W.2d 529
    (2001).
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    on any instrument in writing, or on settlement of the
    account from the day the balance shall be agreed upon,
    on money received to the use of another and retained
    without the owner’s consent, express or implied, from
    the receipt thereof, and on money loaned or due and
    withheld by unreasonable delay of payment. Unless oth-
    erwise agreed or provided by law, each charge with
    respect to unsettled accounts between parties shall bear
    interest from the date of billing unless paid within thirty
    days from the date of billing.
    The court observed that Midwest sent a payment request to
    Roskop Dairy which bore a date of October 14, 2008, but there
    was no evidence of when it was actually sent. Therefore, the
    court utilized the date of November 1, because Roskop Dairy
    admitted that the outstanding principal was owed to Midwest
    as of November 1. The court utilized the rate of 8 percent per
    annum rather than the statutory 12 percent, because 8 percent
    was what Midwest had requested. The court did not expressly
    discuss whether there had been a “reasonable controversy”
    over the amount due to Midwest.3
    ASSIGNMENTS OF ERROR
    Roskop Dairy asserts that the district court erred by (1)
    excluding the testimony of Wailes, (2) denying Roskop Dairy’s
    motion to compel, (3) granting the defendants’ motions for
    summary judgment, and (4) awarding prejudgment interest
    to Midwest.
    STANDARD OF REVIEW
    [1,2] We review de novo whether the trial court applied the
    correct legal standards for admitting an expert’s testimony.4
    We review for abuse of discretion how the trial court applied
    3
    See, e.g., Wilson Concrete Co. v. A. S. Battiato Constr. Co., 
    196 Neb. 185
    ,
    188, 
    241 N.W.2d 819
    , 821 (1976).
    4
    King v. Burlington Northern Santa Fe Ry. Co., 
    277 Neb. 203
    , 
    762 N.W.2d 24
    (2009).
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    the appropriate standards in deciding whether to admit or
    exclude an expert’s testimony.5
    [3] In reviewing a summary judgment, an appellate court
    views the evidence in the light most favorable to the party
    against whom the judgment was granted and gives that
    party the benefit of all reasonable inferences deducible from
    the evidence.6
    [4] Generally, the control of discovery is a matter for
    judicial discretion, and decisions regarding discovery will be
    upheld on appeal in the absence of an abuse of discretion.7
    [5] Prejudgment interest may be awarded only as provided
    in Neb. Rev. Stat. § 45-103.02 (Reissue 2010), and whether
    prejudgment interest should be awarded is reviewed de novo
    on appeal.8
    ANALYSIS
    Exclusion of Wailes’ Testimony and Whether
    There Was M aterial Issue of Fact
    [6,7] The central question in this case is whether we should
    affirm the district court’s order of summary judgment for
    the defendants. A motion for summary judgment shall be
    granted where there is no genuine issue as to any material
    fact and the moving party is entitled to judgment as a mat-
    ter of law.9 Failure of proof concerning an essential element
    of the nonmoving party’s case necessarily renders all other
    facts immaterial.10
    5
    Id.
    6
    Rent-A-Roofer v. Farm Bureau Prop. & Cas. Ins. Co., 
    291 Neb. 786
    , 
    869 N.W.2d 99
    (2015).
    7
    Farmington Woods Homeowners Assn. v. Wolf, 
    284 Neb. 280
    , 
    817 N.W.2d 758
    (2012).
    8
    Countryside Co-op v. Harry A. Koch Co., 
    280 Neb. 795
    , 
    790 N.W.2d 873
          (2010).
    9
    See Rent-A-Roofer v. Farm Bureau Prop. & Cas. Ins. Co., supra note 6.
    10
    See Celotex Corp. v. Catrett, 
    477 U.S. 317
    , 
    106 S. Ct. 2548
    , 
    91 L. Ed. 2d 265
    (1986).
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    [8-10] A party moving for summary judgment makes a
    prima facie case for summary judgment by producing enough
    evidence to demonstrate that the movant is entitled to judg-
    ment if the evidence were uncontroverted at trial.11 Once the
    moving party makes a prima facie case, the burden shifts to
    the party opposing the motion to produce admissible contra-
    dictory evidence showing the existence of a material issue of
    fact that prevents judgment as a matter of law.12 Conclusions
    based on guess, speculation, conjecture, or a choice of pos-
    sibilities do not create material issues of fact for the purposes
    of summary judgment13; the evidence must be sufficient to
    support an inference in the nonmovant’s favor without the fact
    finder engaging in guesswork.14
    The defendants made a prima facie case for summary
    judgment through expert testimony that poor maintenance of
    the vents in the claws was the proximate cause of the units
    detaching under vacuum and, thus, of any mastitis resulting
    therefrom. Without endorsing the sufficiency of the evidence
    on any other aspect of Roskop Dairy’s case, we focus our
    analysis on this element of mechanical causation. Doing so,
    we conclude that Roskop Dairy failed to produce admissible
    contradictory evidence creating a material issue of fact to rebut
    the defend­ants’ prima facie case.
    Wailes neither purported to opine on the mechanical cause
    of the units detaching under vacuum, nor was he qualified
    to do so. And Roskop Dairy did not present other sufficient
    circumstantial evidence that could lead a reasonable person to
    accept its theory that the Dematron was the proximate cause
    11
    Chicago Lumber Co. of Omaha v. Selvera, 
    282 Neb. 12
    , 
    809 N.W.2d 469
          (2011).
    12
    See, Borrenpohl v. DaBeers Properties, 
    276 Neb. 426
    , 
    755 N.W.2d 39
          (2008); New Tek Mfg. v. Beehner, 
    270 Neb. 264
    , 
    702 N.W.2d 336
    (2005).
    13
    Marksmeier v. McGregor Corp., 
    272 Neb. 401
    , 
    722 N.W.2d 65
    (2006);
    Richards v. Meeske, 
    268 Neb. 901
    , 
    689 N.W.2d 337
    (2004).
    14
    C.E. v. Prairie Fields Family Medicine, 
    287 Neb. 667
    , 
    844 N.W.2d 56
          (2014).
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    of the purported injury. As will be explained in more detail
    below, we agree with the district court that Roskop Dairy’s
    reliance on the malfunction theory is misplaced, because it
    is limited to proving a specific defect through circumstantial
    evidence and because Roskop Dairy failed to present evidence
    that could establish the elements of the malfunction theory.
    Any other circumstantial evidence that Roskop Dairy relies on
    to rebut the defendants’ prima facie case for summary judg-
    ment amounts to speculative reasoning based on observations
    of a temporal correlation.
    [11] All implied warranty theories of recovery and strict
    liability claims for manufacturing defect, design defect, or fail-
    ure to warn seek to recover for a “defect.”15 Express warranty
    claims are not merged with implied warranty claims or strict
    liability claims due to the “‘dickered’” aspects of the indi-
    vidual bargain,16 but express warranty claims, like implied war-
    ranty theories and strict liability claims, require a showing that
    the goods were defective.17 While a “defect” traditionally falls
    under the category of either a design, manufacturing, or warn-
    ing defect, “defective” installation is also cognizable under the
    Uniform Commercial Code’s breach of warranty theories when
    the installation is incident to the sale; in other words, when the
    purchase is for a system that is dependent upon proper instal-
    lation.18 And the user of a product may also assert a cause of
    action for negligent installation concurrently with actions under
    express and implied warranty theories.19
    [12-14] Whether a plaintiff is proceeding under negligence,
    defect theories, or breach of express warranty, proximate cause
    15
    See Freeman v. Hoffman-La Roche, Inc., 
    260 Neb. 552
    , 
    618 N.W.2d 827
          (2000).
    16
    
    Id. at 574,
    618 N.W.2d at 844.
    17
    Genetti v. Caterpillar, Inc., supra note 2.
    18
    See, Mennonite Deaconess Home & Hosp. v. Gates Eng’g Co., 
    219 Neb. 303
    , 
    363 N.W.2d 155
    (1985); 3 American Law of Products Liability 3d
    § 37:12 (2015).
    19
    3 American Law of Products Liability 3d, supra note 18.
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    is a necessary element of the plaintiff’s case.20 Proximate cause
    is the cause that in a natural and continuous sequence unbro-
    ken by an efficient intervening cause, produces the injury,
    and without which the injury would not have occurred.21 To
    establish proximate cause, the plaintiff must meet three basic
    requirements: (1) Without the negligent action, the injury
    would not have occurred, commonly known as the “but for”
    rule or “cause in fact”; (2) the injury was a natural and prob-
    able result of the negligence; and (3) there was no efficient
    intervening cause.22
    [15] In this case, proving the elements of defect/negligence
    and proximate cause involves the mechanical functioning of
    a dairy farm milking system and its various component parts.
    Such technical matters are outside the scope of ordinary expe-
    rience. Findings of fact as to technical matters beyond the
    scope of ordinary experience are usually not warranted in the
    absence of expert testimony supporting such findings.23
    Hunt testified that the clogged and upside-down vents
    reported by Nissen and Farrier were the cause of the milking
    units detaching under vacuum. Roskop presented no reliable
    expert opinion to the contrary. Roskop admitted that he was
    not an expert on milking machines. Wailes likewise stated
    20
    See, Powell v. Harsco Corp., 
    209 Ga. App. 348
    , 
    433 S.E.2d 608
    (1993); 1
    American Law of Products Liability 3d § 4:1 (2007).
    21
    See, Stahlecker v. Ford Motor Co., 
    266 Neb. 601
    , 
    667 N.W.2d 244
    (2003);
    Pendleton Woolen Mills v. Vending Associates, Inc., 
    195 Neb. 46
    , 
    237 N.W.2d 99
    (1975).
    22
    See, Hughes v. School Dist. of Aurora, 
    290 Neb. 47
    , 
    858 N.W.2d 590
          (2015); Belgum v. Mitsuo Kawamoto & Assoc., 
    236 Neb. 127
    , 
    459 N.W.2d 226
    (1990); Daniels v. Andersen, 
    195 Neb. 95
    , 
    237 N.W.2d 397
    (1975).
    23
    See, McVaney v. Baird, Holm, McEachen, 
    237 Neb. 451
    , 
    466 N.W.2d 499
          (1991); Overland Constructors v. Millard School Dist., 
    220 Neb. 220
    , 
    369 N.W.2d 69
    (1985). See, also, Green v. Box Butte General Hosp., 
    284 Neb. 243
    , 
    818 N.W.2d 589
    (2012); State v. Aguilar, 
    268 Neb. 411
    , 
    683 N.W.2d 349
    (2004); Eiting v. Godding, 
    191 Neb. 88
    , 
    214 N.W.2d 241
    (1974);
    Clark v. Village of Hemingford, 
    147 Neb. 1044
    , 
    26 N.W.2d 15
    (1947).
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    clearly that he was not an expert in the design, installation,
    diagnosis, settings, or repair of milking machine equipment.
    Wailes stated that he did not know what, if anything, was
    wrong with the Dematron and had no opinion about the param-
    eter settings.
    Roskop points out that Wailes confirmed that “a properly
    operating detacher system” does not “come off under pressure
    as described by . . . Roskop.” This statement, in combination
    with Roskop’s testimony, may support the occurrence of some
    kind of malfunction of the milking system. But this was not
    an opinion as to whether the Dematron was the cause of that
    malfunction. To the contrary, Wailes acknowledged that there
    were many possible mechanical causes of the units coming off
    under vacuum, which have nothing to do with the Dematron.
    Wailes agreed that it would not be “scientific reasoning” to
    conclude that the Dematron was responsible for the claws’
    detaching under vacuum.
    Even if Wailes had been qualified to opine on which com-
    ponent part of the milking system caused the units to detach
    under vacuum, and had actually attempted to do so, such opin-
    ion would be unreliable under Schafersman v. Agland Coop.24
    The expert must have “good grounds” for his or her belief “in
    every step of the analysis.”25 The term “good grounds” means
    an inference or assertion derived by scientific method and sup-
    ported by appropriate validation.26
    [16] Wailes testified, “[M]y analysis is that there had to be
    some event to trigger somatic cell counts to take that much
    of a spike” and “[m]y main concern at the time was the tim-
    ing of the events, and the timing of the events match up to
    the installation.” It is well settled that a causation opinion
    based solely on a temporal relationship is not derived from the
    24
    Schafersman v. Agland Coop, supra note 1.
    25
    King v. Burlington Northern Santa Fe Ry. Co., supra note 
    4, 277 Neb. at 227
    , 762 N.W.2d at 43.
    26
    
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    scientific method and is therefore unreliable.27 Such an opinion
    is also unreliable because it is not based upon sufficient facts
    or data.28
    An expert can challenge hypotheses formulated through the
    observation of association29 or utilize a challenge/­dechallenge/
    rechallenge methodology, or the expert can systematically
    eliminate other reasonably probable causes in conjunction with
    observation of temporal correlation.30 But the reliability of
    such methodologies to support a causation opinion is directly
    related to the degree of scientific rigor.31 Wailes’ assertion
    that “when you try to eliminate events that could occur dur-
    ing that period of time, the one that you can’t eliminate is the
    installation of new equipment that was not working properly
    at the time,” and his further assertions that the feed had not
    changed, that Roskop had a good reputation, and that Roskop
    had unspecified protocols in place, demonstrate little scientific
    rigor. Furthermore, this testimony concerns, at most, alternate
    etiologies of mastitis and not the alternate mechanical causes
    of the malfunction. Thus, to the extent that Roskop makes an
    argument that the court should have admitted Wailes’ testimony
    for purposes of mechanical causation, we find that the district
    court did not err.
    Roskop alternatively argues that expert testimony is not
    required to create a material issue of fact rebutting the
    27
    See, Porter v. Whitehall Laboratories, Inc., 
    9 F.3d 607
    (7th Cir. 1993);
    Derzavis v. Bepko, 
    766 A.2d 514
    (D.C. 2000); Terry v. Bd. of Mental
    Retardation, 
    165 Ohio App. 3d 638
    , 
    847 N.E.2d 1246
    (2006), reversed in
    part on other grounds sub nom. Terry v. Caputo, 
    15 Ohio St. 3d 351
    , 
    875 N.E.2d 72
    (2007). See, also, e.g., Schafersman v. Agland Coop, supra note
    1; Carlson v. Okerstrom, 
    267 Neb. 397
    , 
    675 N.W.2d 89
    (2004).
    28
    King v. Burlington Northern Santa Fe Ry. Co., supra note 4.
    29
    See 
    id. 30 See
    Heller v. Shaw Industries, Inc., 
    167 F.3d 146
    (3d Cir. 1999). See, also,
    Carlson v. Okerstrom, supra note 27.
    31
    See McClain v. Metabolife Intern., Inc., 
    401 F.3d 1233
    (11th Cir. 2005).
    See, also, Glastetter v. Novartis Pharmaceuticals Corp., 
    252 F.3d 986
    (8th
    Cir. 2001).
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    defendants’ prima facie case for summary judgment. In making
    this argument, Roskop apparently relies on the “malfunction
    theory.” The malfunction theory is based on the same principle
    underlying res ipsa loquitur, which permits a fact finder to
    infer negligence from the circumstances of the incident, with-
    out resort to direct evidence of the wrongful act.32
    [17] Under the malfunction theory, also sometimes called
    the indeterminate defect theory or general defect theory,33 a
    plaintiff may prove a product defect circumstantially, without
    proof of a specific defect, when (1) the incident causing the
    harm was of a kind that would ordinarily occur only as a result
    of a product defect and (2) the incident was not, in the particu-
    lar case, solely the result of causes other than a product defect
    existing at the time of sale or distribution.34
    The malfunction theory should be utilized with the utmost
    of caution. Although some circumstances may justify the use
    of the malfunction theory to bridge the gap caused by miss-
    ing evidence, the absence of evidence does not make a fact
    more probable but merely lightens the plaintiff’s evidentiary
    burden despite the fact that the missing evidence might well
    have gone either way, and this rationale is too often subject
    to misapplication by courts in situations in which evidence is
    actually available.35
    32
    Restatement (Third) of Torts: Products Liability § 3, comment a. (1998).
    33
    See, 
    id., § 3;
    David G. Owen, Manufacturing Defects, 
    53 S.C. L
    . Rev. 851
    (2002). See, also, e.g., Sochanski v. Sears, Roebuck and Co., 
    621 F.2d 67
          (3d Cir. 1980); Stewart v. Ford Motor Co., 
    553 F.2d 130
    (D.C. Cir. 1977);
    Higgins v. General Motors Corp., 
    287 Ark. 390
    , 
    699 S.W.2d 741
    (1985);
    Wakabayashi v. Hertz, 
    66 Haw. 265
    , 
    660 P.2d 1309
    (1983); Gillespie v. R.
    D. Werner Co., 
    71 Ill. 2d 318
    , 
    375 N.E.2d 1294
    , 17 Ill Dec. 10 (1978);
    Stackiewicz v. Nissan Motor Corp., 
    100 Nev. 443
    , 
    686 P.2d 925
    (1984);
    Moraca v. Ford Motor Co., 
    66 N.J. 454
    , 
    332 A.2d 599
    (1975); Brownell v.
    White Motor Corp., 
    260 Or. 251
    , 
    490 P.2d 184
    (1971).
    34
    Genetti v. Caterpillar, Inc., supra note 2; Restatement, supra note 32, § 3.
    35
    See Metro. Property & Cas. Ins. Co. v. Deere & Co., 
    302 Conn. 123
    , 
    25 A.3d 571
    (2011).
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    We have explained that as a matter of policy we allow
    circumstantial proof of a product defect without evidence of
    the specific defect because in many instances the dealer or
    manufacturer has either purposefully or inadvertently tam-
    pered with the evidence. Further, in light of the technological
    complexity in proving a specific defect, “forcing consumers to
    identify the cause, rather than the effect, of a defect would be
    unrealistically burdensome.”36
    The malfunction theory is narrow in scope. The malfunction
    theory simply provides that it is not necessary for the plaintiff
    to establish a specific defect so long as there is evidence of
    some unspecified dangerous condition or malfunction from
    which a defect can be inferred37—the malfunction itself is cir-
    cumstantial evidence of a defective condition.38 The malfunc-
    tion theory does not alter the basic elements of the plaintiff’s
    burden of proof and is not a means to prove proximate cause
    or damages.39
    Other courts have set forth a nonexhaustive list of the kind
    of circumstantial evidence that may be used to support a rea-
    sonable inference of a specific defect. In DeWitt v. Eveready
    Battery Co., Inc.,40 for example, the court illustrated six evi-
    dentiary factors that a plaintiff may present to create a genuine
    issue of fact on the element of defect through circumstantial
    evidence: (1) the malfunction of the product; (2) expert tes-
    timony as to a possible cause or causes; (3) the timeframe of
    the malfunction’s occurrence after the plaintiff first obtained
    the product and other relevant history of the product, such
    as its age and prior usage by the plaintiff and others, includ-
    ing evidence of misuse, abuse, or similar relevant treatment
    36
    Genetti v. Caterpillar, Inc., supra note 
    2, 261 Neb. at 114
    , 621 N.W.2d. at
    542.
    37
    1 American Law of Products Liability 3d, supra note 20, § 1:15 (2013).
    38
    Ducko v. Chrysler Motors Corp., 
    433 Pa. Super. 47
    , 
    639 A.2d 1204
    (1994).
    39
    See Sochanski v. Sears, Roebuck and Co., supra note 33.
    40
    DeWitt v. Eveready Battery Co., Inc., 
    355 N.C. 672
    , 
    565 S.E.2d 140
          (2002).
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    before it reached the defendant; (4) similar incidents, when
    accompanied by proof of substantially similar circumstances
    and reasonable proximity in time; (5) elimination of other pos-
    sible causes of the accident; and (6) proof tending to establish
    that such an accident would not occur absent a manufactur-
    ing defect.
    Roskop relies on Genetti v. Caterpillar, Inc., in which we
    applied the principles of the malfunction theory and some of
    these factors to conclude that the circumstantial evidence of
    a defect was sufficient to support a verdict in the plaintiffs’
    favor.41 The plaintiffs in Genetti sought recovery for the total
    failure of their truck’s engine. Subsequent to purchasing the
    truck new, multiple engine failures had occurred. The defend­
    ant had first repaired the engine and, upon subsequent failures,
    replaced it. In replacing the engine, the defendant utilized some
    components from the old engine. The defendant did not keep
    records of which components of the engine were replaced and
    which were reused. Eventually, the truck was sold, and the
    defendant replaced the engine again after another engine fail-
    ure subsequent to the purchase.
    The plaintiffs’ expert witness, a mechanic, admitted he was
    not an expert in engine design, but illustrated his expertise in
    repairing, rebuilding, and overhauling the kind of engine at
    issue. The mechanic reviewed documentation of the repairs,
    photographs, and interviews, and concluded that a coolant
    leak caused the engine failures. The mechanic negated alter-
    nate, reasonably possible causes of the engine failures. The
    mechanic was unsure whether the coolant leak was specifi-
    cally due to a cracked head, cracked head gasket, or some
    other failure allowing the intrusion of coolant. He testified,
    however, that the uncontroverted testimony concerning the
    use of the truck was not a misuse that should have resulted in
    engine failure.
    We held that because the plaintiffs presented evidence elim-
    inating abuse or misuse as the alternate cause of the engine
    41
    Genetti v. Caterpillar, Inc., supra note 2.
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    failure, it was reasonable for a jury to conclude that if the fail-
    ure was not due to improper use of the truck, then it was due
    to a defect, such as one of those suggested by the mechanic.42
    We held that the plaintiffs were not required to prove the spe-
    cific defect that caused the failures in order to prove that the
    engine was defective.43
    But more apposite to the facts of this case is Wilgro, Inc.
    v. Vowers & Burback.44 In Wilgro, Inc., although (unlike here)
    there was direct evidence of a specific defect, we held that the
    circumstantial evidence was insufficient to support a finding of
    proximate cause. The defendant in Wilgro, Inc. had provided
    the plaintiff with feed supplements for the plaintiff’s cattle that
    contained slightly higher levels of nonprotein nitrogen, urea,
    than warrantied. Shortly after obtaining the feed, the cattle
    became sick. Some eventually died. Autopsies on some of the
    cattle were performed, and they were found to have died of
    urea poisoning.
    Other causation theories unrelated to the defect and sup-
    ported by the record could account for the poisoning. For
    instance, given the method of merely spreading the supplement
    on the bottom of a truck and pouring silage on top where the
    cattle “free fed,” the feed could have been improperly mixed
    with the supplement. Or, some cows could have eaten more
    feed than they were allotted. Furthermore, the plaintiff’s own
    immature silage could account for the symptoms observed
    in the majority of the animals that the plaintiff claimed had
    been injured.
    [18,19] We explained that circumstantial evidence is not
    sufficient to sustain a verdict that depends solely thereon
    unless the circumstances proved by the evidence are of such a
    nature and so related to each other that the conclusion reached
    by the jury is the only one that can fairly and reasonably be
    42
    See 
    id. 43 Id.
    44
    Wilgro, Inc. v. Vowers & Burback, 
    190 Neb. 369
    , 
    208 N.W.2d 698
    (1973).
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    drawn therefrom.45 Where, instead, under the facts viewed in a
    light most favorable to the nonmoving party, the nonexistence
    of the fact to be inferred is just as probable as its existence, the
    conclusion that it exists is a matter of speculation, surmise, and
    conjecture, and a jury will not be permitted to draw it.46 We
    concluded in Wilgro, Inc. that the plaintiff had failed to adduce
    evidence that would lead the reasonable person to accept the
    plaintiff’s theory of causation over those theories presented by
    the defendant.
    In Pendleton Woolen Mills v. Vending Associates, Inc.,47 a
    negligence case, we similarly found the circumstantial evi-
    dence to be insufficient for any determination of proximate
    cause in the plaintiff’s favor to rise above speculation. The
    plaintiff’s building had been damaged by the flooding of a
    sticky substance. A large amount of water and syrup was found
    on the floor in the vicinity of a soft drink machine, which was
    the apparent source of the flooding. The machine obtained its
    water supply from a water pipe in the building, to which it
    was connected by copper tubing. The defendant was allegedly
    responsible for the maintenance of the machine.
    We found “a total lack of evidence establishing that any
    negligence . . . was the ‘proximate cause’ of either the leak
    or the damages; or to state it more accurately, that there was
    any ‘causation in fact’ between the alleged negligence, and
    the occurrence and the water damage.”48 Only one nonexpert
    witness reported a hearsay statement loosely attributing the
    leak to a malfunctioning shutoff valve. And there was no
    proof that the absence of regular inspection was a substan-
    tial factor in causing the valve to malfunction, if it indeed
    did. Nor was there evidence that but for the absence of such
    inspection, the leak would not have occurred. In particular,
    45
    
    Id. 46 See
    Ehler et ux v. Portland Gas & Coke Co., 
    223 Or. 28
    , 
    352 P.2d 1102
          (1960).
    47
    Pendleton Woolen Mills v. Vending Associates, Inc., supra note 21.
    48
    
    Id. at 50,
    237 N.W.2d at 102.
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    there was no evidence indicating the location of the shutoff
    valve in the machine and whether a leak could be detected.
    Again, we said that speculation and conjecture are not suf-
    ficient to establish causation; there must be something more
    that will lead a reasonable mind to one conclusion rather
    than another.49
    In considering Roskop Dairy’s argument that the malfunc-
    tion theory applies, we first note that there is no apparent loss
    of the evidence of a specific defect, because there is a record
    of the parameter settings. Indeed, from these records, Roskop
    has suggested a very specific theory that the detach delay
    setting of 3 seconds was defective and negligent and that it
    should have been 10 seconds, the setting it was changed to in
    late July 2008. While we have found little case law specifi-
    cally addressing whether the malfunction theory applies when
    there is no loss of evidence or when there is an allegation of
    a specific defect, we find no cases that have done so. And we
    observe that the related doctrine of res ipsa loquitur does not
    apply when specific acts of negligence are alleged or there is
    evidence of the precise cause of the accident.50
    Assuming that the malfunction theory can be utilized when
    there has been no loss of evidence relating to the alleged spe-
    cific defect, Roskop presented insufficient evidence to estab-
    lish a material issue of fact supporting the malfunction theory.
    Roskop presented no reliable evidence that the incident causing
    the harm was of a kind that would ordinarily occur only as a
    result of a product defect, as he had no expert on milking sys-
    tems. And he presented no reliable evidence negating causes
    other than the alleged product defect—despite undisputed evi-
    dence that detachment under vacuum could have multiple pos-
    sible mechanical sources.51 Roskop did not even present evi-
    dence negating Nissen’s and Farrier’s testimony that the vents
    49
    Pendleton Woolen Mills v. Vending Associates, Inc., supra note 21.
    50
    See Maly v. Arbor Manor, Inc., 
    225 Neb. 276
    , 
    404 N.W.2d 419
    (1987).
    51
    See, Genetti v. Caterpillar, Inc., supra note 2; Restatement, supra note 32,
    § 3.
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    of the lenses had been placed upside down and that nonvented
    lenses had been placed in the claws.
    [20,21] In any event, the malfunction theory would not
    serve to create a material issue on the element of proxi-
    mate cause, because it is a theory only utilized to prove the
    element of defect.52 Roskop Dairy seeks more than just a
    bridge over the gap of difficult-to-obtain and highly techni-
    cal evidence of a specific defect. Roskop attempts to create
    a material issue of fact on little more than his observation of
    a temporal correlation. But the line between impermissible
    speculation and reasonable inferences is drawn by the laws
    of logic.53 And reasoning causation from temporal correlation
    represents a logical fallacy. A conclusion based upon such
    reasoning is not a reasonable inference but is mere specula-
    tion and conjecture.54
    We find no merit to Roskop’s argument that Hunt’s testi-
    mony confirming that the settings for the detach delay were
    changed from 3 seconds to 10 seconds rebuts the defendants’
    prima facie case. It would be speculative to derive any conclu-
    sion as to either negligence/defect or proximate cause based on
    the record of the parameter settings without an expert opinion
    interpreting those settings in the larger context of the milking
    system. Roskop Dairy’s conclusion based on the correlation of
    the 3-second setting to detachment under vacuum and of the
    10-second setting to no detachment under vacuum remains at
    its core an application of the logical fallacy that correlation
    equals causation.
    52
    See, White v. Mazda Motor of America, Inc., 
    313 Conn. 610
    , 
    99 A.3d 1079
          (2014); Barnish v. KWI Bldg. Co., 
    916 A.2d 642
    (Pa. 2007).
    53
    Tose v. First Pennsylvania Bank, N.A., 
    648 F.2d 879
    (3d Cir. 1981),
    abrogated on other grounds, Griggs v. Provident Consumer Discount Co.,
    
    459 U.S. 56
    , 
    103 S. Ct. 400
    , 
    74 L. Ed. 2d 225
    (1982).
    54
    See, Sunward Corp. v. Dun & Bradstreet, Inc., 
    811 F.2d 511
    (10th Cir.
    1987); Loesch v. United States, 
    645 F.2d 905
    (Ct. Cl. 1981); Dodge Motor
    Trucks, Inc. v. First Nat. Bank of Omaha, 
    519 F.2d 578
    (8th Cir. 1975);
    Genesee M. B. & T. Co. v. Payne, 
    6 Mich. App. 204
    , 
    148 N.W.2d 503
          (1967).
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    At oral arguments, Roskop Dairy also suggested that sum-
    mary judgment was improper because cross-examination of
    Hunt at trial might lead to a more favorable and direct admis-
    sion regarding the Dematron settings and their connection to
    the detachment under vacuum. In two depositions, Roskop
    Dairy has failed to obtain an opinion from Hunt that the
    Dematron settings during the relevant time period were in any
    way improper or a substantial factor in causing the units to
    detach under vacuum. Roskop’s hope that this testimony might
    change at trial is insufficient to rebut the defendants’ prima
    facie case for summary judgment.
    Under the malfunction theory or otherwise, Roskop Dairy
    failed to present evidence from which a jury could deter-
    mine, without resorting to speculation, that the Dematron was
    the proximate cause of the alleged injury to Roskop Dairy’s
    cows. The district court accordingly did not err in granting the
    defendants summary judgment. Although we share the district
    court’s concerns over the lack of evidence that the Dematron
    was defectively or negligently installed and the lack of reli-
    able evidence causally linking the detachment under vacuum
    to the medical condition of mastitis, we need not examine
    those aspects of the district court’s ruling in order to affirm
    its decision.
    Considering Testimony
    Not in Evidence
    We find no merit to Roskop Dairy’s assertion that we
    should reverse the district court’s order because it errone-
    ously relied on facts not in evidence when it granted sum-
    mary judgment. Roskop argues that in reasoning that there are
    several causes of mastitis, the district court erroneously relied
    on Gorden’s affidavit, which was not entered into evidence.
    Roskop argues that, even “more egregiously,” the district court
    relied on Wailes’ excluded testimony and upon the deposition
    of Slattery, which was admitted for limited purposes only.55
    55
    Brief for appellant at 28.
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    Roskop argues that the district court could not rely on any
    aspect of Wailes’ testimony, because neither party reoffered
    it for summary judgment. Finally, Roskop characterizes the
    district court’s order as expressing an improper factual finding
    that other factors could have contributed to or caused mastitis
    in the herd.
    It is unclear how Roskop believes it helpful to argue that
    Wailes’ deposition was not in evidence for purposes of sum-
    mary judgment. The absence of Wailes’ testimony in its entirety
    provides only less evidence from which we could conclude
    there was a material issue of fact. And such argument ren-
    ders fruitless Roskop Dairy’s argument that Wailes’ testimony
    should not have been excluded.
    Furthermore, the alternate causes of mastitis that Roskop
    believes the court erred in considering were generally listed
    in other admitted testimony, such as Roskop’s deposition
    and the limited receipt of Slattery’s deposition. A summary
    judgment hearing is similar to a bench trial of an action at
    law; thus, ordinarily, the erroneous admission of evidence in
    a summary judgment hearing is not reversible error if other
    relevant evidence, admitted without objection or properly
    admitted over objection, sustains the trial court’s necessary
    factual findings.56
    Regardless, none of Roskop Dairy’s arguments on this
    assignment of error concern the absence of reliable evidence
    rebutting the defendants’ prima facie case that improper main-
    tenance by Roskop Dairy employees of the physical compo-
    nents of the milking system was the proximate cause of the
    malfunction. Therefore, these arguments are not grounds for
    reversal under our reasoning set forth above.
    Denying Discovery
    Roskop Dairy also argues that the district court erred in
    denying its motion to compel. Roskop Dairy argues vaguely
    56
    John Markel Ford v. Auto-Owners Ins. Co., 
    249 Neb. 286
    , 
    543 N.W.2d 173
    (1996).
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    that there is a series of correspondence listed on the privilege
    log between an employee of Midwest and its designated expert
    witness. Roskop Dairy further argues generally that it was
    entitled to discover underlying facts contained in privileged
    documents, such as parameter settings and changes, facts
    regarding the operation and maintenance of the system, and
    facts relating to the investigations of the malfunction of the
    system. Lastly, Roskop Dairy asserts broadly that information
    and parameter settings gathered by Hunt in the ordinary course
    of business were not privileged.
    [22] The party asserting error in a discovery ruling bears
    the burden of showing that the ruling was an abuse of dis-
    cretion.57 For our review, Roskop Dairy requested only that
    sealed exhibit 9 be included in the bill of exceptions. It
    is incumbent upon the party appealing to present a record
    which supports the errors assigned. Neb. Rev. Stat. § 25-1140
    (Reissue 2008) and Neb. Ct. R. App. P. § 2-105(B)(1)(b) (rev.
    2010) place the burden on the appellant to file a praecipe
    identifying the matter to be contained in the bill of excep-
    tions. Thus, we consider Roskop’s assignment of error only
    as pertains to exhibit 9.
    After an in camera review, the district court found that the
    documents contained in exhibit 9 were protected by attorney-
    client privilege and work-product privilege. The court also
    noted that GEA had produced for Roskop Dairy its most
    knowledgeable witness, Hunt, to be deposed on the topics
    contained in the deposition notice duces tecum attached to
    Roskop Dairy’s motion to compel discovery. Further, the
    court found that GEA had produced the records required by
    Roskop Dairy’s discovery request, except for those protected
    by privilege, but that Roskop Dairy had difficulty opening
    certain computer records and that Hunt did not have them
    all with him during his deposition. Because of this, the
    court allowed Roskop Dairy great “latitude in discovery”
    and ordered that Roskop Dairy be able to reconvene the
    57
    U.S. Bank Nat. Assn. v. Peterson, 
    284 Neb. 820
    , 
    823 N.W.2d 460
    (2012).
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    deposition of Hunt and that Hunt should have with him cop-
    ies of any records he relied on for his testimony. That second
    deposition occurred, and Hunt brought with him records of
    the Dematron parameter settings.
    We find no abuse of discretion in the district court’s order
    partially denying Roskop Dairy’s motion to compel. There is
    no evidence that Roskop Dairy was denied discovery of rel-
    evant underlying facts or business records pertaining to param-
    eter settings or to any changes or facts regarding the operation
    and maintenance of the system. Furthermore, the court did
    not abuse its discretion in finding the documents contained in
    sealed exhibit 9 to be protected by the attorney-client privilege
    and the work-product privilege.
    We have recognized that it is difficult to show that a party
    has been prejudiced by a discovery order, or that the question
    is not moot; and the harmless error doctrine, together with
    the broad discretion the discovery rules vest in the trial court,
    will bar reversal save under very unusual circum­      stances.58
    This case is no exception. We find no merit to Roskop
    Dairy’s assignment of error concerning the motion to com-
    pel discovery.
    Prejudgment Interest
    Finally, we turn to Roskop Dairy’s argument that the district
    court erred in granting Midwest prejudgment interest on its
    counterclaim for the unpaid amount of the purchase agree-
    ment. Prejudgment interest may be awarded only as provided
    in § 45-103.02, and whether prejudgment interest should be
    awarded is reviewed de novo on appeal.59
    [23] A claim is liquidated for purposes of prejudgment
    interest when there is no reasonable controversy as to both the
    amount due and the plaintiff’s right to recover.60 The amount
    58
    Brozovky v. Norquest, 
    231 Neb. 731
    , 
    437 N.W.2d 798
    (1989).
    59
    Countryside Co-op v. Harry A. Koch Co., supra note 8.
    60
    Brook Valley Ltd. Part. v. Mutual of Omaha Bank, 
    285 Neb. 157
    , 
    825 N.W.2d 779
    (2013). See, also, § 45-103.02(2).
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    due was uncontroverted. But we conclude that, given the tech-
    nical complexity of the matters at issue, until discovery was
    completed, there was a reasonable controversy over Roskop
    Dairy’s right to recover. The fact that summary judgment was
    properly granted is not decisive of whether there was until
    that point a reasonable controversy over a plaintiff’s right to
    recover.61 We therefore reverse the district court’s order grant-
    ing prejudgment interest on Midwest’s counterclaim.
    CONCLUSION
    The opponent of a motion for summary judgment must be
    given the benefit of every reasonable inference from the evi-
    dence, but not inferences based on guess or speculation.62 The
    defendants made a prima facie case that there was no issue of
    fact that components other than the Dematron were the proxi-
    mate cause of the detachment under vacuum. Roskop’s eyewit-
    ness observation of a temporal correlation between installation
    of the Dematron and the units detaching under vacuum calls
    for speculation and is insufficient to create an issue of fact on
    the essential element of proximate cause. We therefore affirm
    the order of the district court granting summary judgment for
    the defendants in Roskop Dairy’s action against them. But we
    reverse the district court’s order granting prejudgment interest
    on Midwest’s counterclaim.
    A ffirmed in part, and in part reversed.
    Heavican, C.J., participating on briefs.
    Stephan, J., not participating in the decision.
    Wright, J., not participating.
    61
    See, Countryside Co-op v. Harry A. Koch Co., supra note 8; Dutton-
    Lainson Co. v. Continental Ins. Co., 
    279 Neb. 365
    , 
    778 N.W.2d 433
          (2010).
    62
    See Giordano v. Sherwood, 
    968 A.2d 494
    (D.C. 2009).