The Science & Medicine Behind Mass Tort Litigation
Key Takeaways
- Scientific evidence is the foundation of every mass tort case
- General causation (can a product cause harm?) must be established before individual cases proceed
- Expert witnesses must meet the Daubert reliability standard in federal courts
- Epidemiological studies, toxicology, and clinical data are key evidence types
What Role Does Science Play in Mass Torts?
Mass tort litigation is fundamentally driven by scientific and medical evidence. Before any plaintiff can recover damages, the court must determine two levels of causation: general causation (whether the product is capable of causing the alleged injury) and specific causation (whether it caused this particular plaintiff's injury).
This dual-causation framework makes scientific evidence — epidemiological studies, toxicological analyses, clinical research, and expert testimony — the backbone of mass tort cases.
What Is the Difference Between General and Specific Causation?
General Causation
Can the product cause this type of injury in anyone? This is a population-level question answered through epidemiological studies, animal studies, and mechanistic evidence. Courts often hold "general causation" hearings (Daubert hearings) early in MDL proceedings.
Specific Causation
Did the product cause this plaintiff's specific injury? This requires individual medical evaluation, exposure history, differential diagnosis, and ruling out alternative causes. This is assessed case-by-case.
What Is the Daubert Standard?
In federal courts and most state courts, expert scientific testimony must meet the reliability standards established by the U.S. Supreme Court in Daubert v. Merrell Dow Pharmaceuticals(1993). Under Daubert, judges serve as "gatekeepers" who evaluate whether expert testimony is based on:
- Sufficient facts or data
- Reliable principles and methods
- Proper application of those methods to the case facts
Daubert hearings are often pivotal in mass tort litigation. If plaintiffs' experts are excluded, the case may be dismissed. If they survive Daubert, the case typically proceeds to trial or settlement negotiations.
What Types of Scientific Evidence Are Used?
Epidemiological Studies
Studies that examine the association between an exposure and a disease in human populations. These are often considered the strongest form of evidence for general causation. Key measures include relative risk, odds ratios, and confidence intervals.
Toxicological Studies
Laboratory and animal studies that examine the biological mechanisms by which a substance can cause harm. While not direct evidence of human injury, toxicology can support causation by demonstrating a plausible biological mechanism.
Clinical & Regulatory Data
FDA adverse event reports, clinical trial data, post-marketing surveillance, and internal company documents all play important roles. Internal documents are particularly powerful when they reveal that a company knew about risks but failed to act.
What Do Expert Witnesses Do in Mass Torts?
Expert witnesses — epidemiologists, toxicologists, oncologists, neurologists, and other specialists — are essential in mass tort cases. They interpret complex scientific data for judges and juries, provide opinions on causation, and are often the most influential voices in bellwether trials. Both sides retain competing experts, and the battle of experts often determines the outcome.