Product Liability Litigation: Evidence, Experts, and Trial Strategy

The documents that most frequently produce punitive damages awards in product liability litigation are the ones the company generated internally when it first learned about the defect, assessed the cost of fixing it, and decided not to.

Rule 30(b)(6) depositions direct the corporate defendant to produce a witness prepared to testify on designated topics, including the company's design and testing process for the specific product, the company's internal reporting of field failures and customer complaints, and any pre-incident regulatory correspondence with the FDA, CPSC, or NHTSA about the product's safety profile. The corporate representative is bound by the company's knowledge on the designated topics, not by the individual witness's personal recollection. Materials reviewed to prepare a Rule 30(b)(6) witness may become discovery targets, although privilege and work-product objections often determine what must actually be produced, and the scope of what is discoverable varies by jurisdiction and the specific circumstances of the case.

FOIA requests to the CPSC, FDA, and NHTSA produce prior consumer complaints, accident reports, testing data submitted in regulatory submissions, and any agency correspondence with the manufacturer about the product's safety record. These public records are not subject to attorney-client privilege, and they frequently reveal that the regulatory agency had been receiving adverse event reports about the same product for years before the plaintiff's injury. Civil litigation evidence and complex litigation practice in product liability cases requires coordinating FOIA requests with private discovery to build a complete timeline of what the company and the regulators knew, and when.

A product liability case without an expert who survives Daubert scrutiny on each essential element is not a case. It is a dismissed case. The expert challenge is not a trial event. It is a case-ending event when the plaintiff's expert is excluded before the jury is seated.

FRE 702, as amended in 2023, requires the proponent of expert testimony to establish by a preponderance of the evidence that the expert's opinion is based on sufficient facts or data, uses reliable principles and methods, and reliably applies those methods to the facts of the case. The 2023 amendment clarified that the court, not the jury, decides admissibility by a preponderance standard, and that an expert whose methodology is plausible but not established as reliable does not survive the gatekeeping inquiry simply because the opinion might be credible to a jury. A Daubert motion that successfully excludes the plaintiff's defect expert removes the foundation for the defect claim. A motion that excludes the causation expert removes the bridge between the defect and the injury.

The standard for surviving Daubert in product cases requires the expert to demonstrate that the methodology used to identify the defect or establish causation has been tested, has been subjected to peer review and publication, has a known or estimable rate of error, and is generally accepted in the relevant scientific or engineering community. An engineer who applied established industry standards and testing protocols, and whose analysis is consistent with published engineering literature on the same failure mode, has built a more defensible foundation than one who used a novel simulation methodology without peer-reviewed validation. Product liability and mass torts and defective products practice requires building the expert witness framework to anticipate the specific Daubert challenge the defendant is most likely to file, rather than treating expert selection as a generic qualification exercise.

Causation in product liability litigation is not a single question. It is two questions that require separate expert analyses, and the failure to address either one leaves a critical element unproven.

General causation asks whether the product, or exposure to the product, is capable of causing the type of harm the plaintiff suffered. This is an epidemiological and scientific question addressed through published studies, biological plausibility analysis, and application of criteria like the Bradford Hill factors, which evaluate the strength, consistency, specificity, temporality, and dose-response gradient of the association between exposure and injury. In pharmaceutical and toxic exposure cases, general causation is frequently the most contested battleground, because defendants with strong general causation challenges can obtain summary judgment without the court ever reaching specific causation.

Specific causation asks whether the product actually caused this plaintiff's injury, given the plaintiff's specific medical history, exposure level, and other risk factors. Specific causation in medical product cases typically requires a treating physician or independent medical expert who can apply differential diagnosis methodology to rule out alternative causes and identify the product as the most probable cause of this plaintiff's specific injury. Mass torts and complex commercial litigation cases require a causation strategy that addresses both levels before discovery closes, because a defendant motion for summary judgment on causation can be filed on either prong independently.

Prior similar incidents evidence is among the most powerful tools available in product liability litigation and among the most contested. It is typically offered to establish notice, knowledge, defect existence, or punitive damages, not character or propensity. Courts generally require substantial similarity between the prior incidents and the plaintiff's incident: the same product, the same failure mode, and comparable use conditions. Defendants challenge this evidence under Rule 403, arguing that even relevant prior incidents create unfair prejudice, confuse the issues, or mislead the jury when the circumstances differ in ways that make the comparison more inflammatory than probative. When prior incidents survive the admissibility challenge, documents showing the company received complaints, warranty claims, or adverse event reports about the same defect before the plaintiff's injury establish that the defendant knew the product was dangerous and chose not to act, which is the foundation of any punitive damages claim.

Class actions and MDLs are distinct mechanisms, and understanding the difference affects how a plaintiff in a multi-party product case evaluates settlement options and controls the trajectory of the claim.

A class action under FRCP Rule 23 resolves claims through a representative plaintiff and a certified class. The named plaintiff's decision to accept or reject a settlement binds all class members who do not opt out, and the Rule 23(b)(3) predominance requirement, which asks whether common questions of law or fact predominate over individual ones, is the primary certification battleground in product defect cases. Manufacturing defect cases, where each plaintiff's specific product must be individually examined, are harder to certify than design defect cases, where the defect is theoretically uniform across the entire product line. An MDL under 28 U.S.C. § 1407 coordinates individual federal lawsuits before one judge for pretrial discovery, expert motions, and bellwether trials, but each plaintiff retains an individual claim. A bellwether verdict in an MDL does not bind other plaintiffs, but it establishes the range of likely outcomes that drives global settlement negotiations.

The choice between class action and MDL affects settlement leverage, claim valuation, and individual plaintiff control. A plaintiff with a severe injury and strong causation evidence may recover more through individual MDL litigation than through a class settlement that averages outcomes across thousands of claimants with varying injury severity. A plaintiff with a less severe injury who faces significant litigation cost and risk may benefit from the certainty of a class settlement or MDL global resolution. Multi-district litigation and class actions and multi-district litigation practice requires evaluating the specific claim's value against the transaction costs and risks of individual litigation before any participation decision is made.

Product liability litigation is driven by expert testimony and corporate documents in ways that distinguish it from most other injury cases. Every essential element, including the existence of the defect, whether a safer alternative design was available, the causal link between the defect and the injury, and the extent of damages, requires qualified expert opinion that must survive a Daubert admissibility challenge before the jury hears it. The defendant is almost always a corporation, which means discovery produces internal documents about what the company knew and when, and those documents frequently reveal prior knowledge of the defect that supports punitive damages. The litigation is expensive to build correctly, and the economics require that the provable damages justify the investment in expert witnesses, document review, and potentially years of litigation.

A Daubert challenge is a motion to exclude an expert witness's testimony on the grounds that it does not satisfy the admissibility standards of FRE 702. Under Daubert, federal trial courts act as gatekeepers who must evaluate whether an expert's methodology is scientifically valid before allowing the jury to hear the opinion. If the plaintiff's defect expert is excluded, the defect element is unproven and the defendant can move for summary judgment. If the causation expert is excluded, the causation element is unproven. Either exclusion, standing alone, can result in dismissal of the entire case before trial. The 2023 amendment to FRE 702 clarified that courts evaluate admissibility by a preponderance standard, making it easier for defendants to argue that a plausible but insufficiently supported expert opinion does not cross the threshold.

Preserve the product in its post-incident condition without cleaning, repairing, or modifying it. Photograph it extensively from multiple angles. Keep all original packaging, including lot numbers and expiration dates. Keep your receipt or credit card records confirming the purchase. Gather all medical records from emergency treatment and follow-up care that document the injury mechanism. Preserve any warranty claims, customer service communications, or prior complaints you made to the manufacturer. If the injury occurred in a workplace or commercial setting, preserve the incident report, maintenance logs, and any OSHA documentation. The product itself and the medical records confirming the injury mechanism are the two most critical items, and both become harder to use as evidence if altered, contaminated, or lost before an expert can examine them.

A class action under FRCP Rule 23 resolves claims through a representative plaintiff and a certified class, and a settlement accepted by the class representative generally binds all class members who did not opt out. An MDL under 28 U.S.C. § 1407 consolidates individual federal cases before one judge for coordinated pretrial proceedings, but each plaintiff keeps an individual claim and is not bound by another plaintiff's settlement decision. In MDL, bellwether trials test a small number of representative cases to establish the likely verdict range and drive global settlement negotiations, without binding the remaining plaintiffs. Whether a specific product injury claim is better pursued through a class action or through MDL depends on the injury severity, the individual causation evidence, and whether the settlement fund's allocation methodology reflects the specific claim's value.