How Experts Can Help Identify Alternative Theories of Causation

In high-stakes litigation, establishing a clear, direct line of causation between an act and the resulting harm is essential. Yet in many cases, the evidence is anything but straightforward. Competing variables, complex systems, or multifactorial injuries often blur causal relationships. Plaintiffs may struggle to prove proximate cause; defendants may seek to shift liability by introducing alternate explanations. In this contested space, expert witnesses play a critical role—not only by supporting or challenging causation claims but by identifying alternative theories of causation that could shift the trajectory of a case.

The Problem of Singular Causation in Complex Litigation

Many legal disputes rely on a single, prevailing narrative of causation. For example, in product liability or toxic tort cases, a plaintiff might assert that a particular exposure caused their illness. But diseases like cancer or neurological damage are rarely monocausal. Similarly, in medical malpractice or construction litigation, adverse outcomes may arise from a confluence of actions, omissions, or external factors.

When courts or juries are presented with only one theory of causation, the risk of incomplete or inaccurate conclusions rises significantly. This is particularly problematic when alternative, equally plausible explanations are available—but overlooked. Without expert input, these alternate theories may remain undiscovered, leaving litigants vulnerable to incomplete assessments of liability or damages.

The Role of Experts in Reframing Causation

Expert witnesses—whether medical professionals, engineers, forensic scientists, or epidemiologists—offer a level of domain-specific knowledge that attorneys and jurors often lack. Their insights can reveal gaps in the prevailing narrative or introduce scientifically grounded alternatives. This can be pivotal in cases involving complex causation, such as:

• Pharmaceutical and medical device litigation, where an expert toxicologist or pharmacologist might argue that a patient’s condition stemmed from underlying disease progression, not the drug in question.
• Environmental exposure cases, in which a geologist or industrial hygienist could demonstrate that a plaintiff’s symptoms were more likely caused by background pollution or unrelated chemical exposure.
• Construction defect claims, where a structural engineer may determine that design flaws, rather than workmanship, triggered a building failure.

By proposing alternative theories of causation, experts can do more than simply rebut opposing testimony—they can reframe the entire narrative of liability.

Shifting Legal Strategies Through Alternative Causation

In both plaintiff and defense strategies, expert-generated alternative causation theories serve distinct but powerful functions.

For the defense, presenting a scientifically credible alternative theory can raise sufficient doubt to avoid liability. For example, in asbestos litigation, defendants often argue that a claimant’s mesothelioma was caused by non-occupational exposures or other co-defendants’ products. These theories must be backed by reliable methodology and adhere to Daubert or Frye standards, but when successfully introduced, they can be case determinative.

For plaintiffs, identifying alternative causation can preempt defense strategies or broaden liability among multiple parties. Consider a motor vehicle accident involving multiple collisions—if a biomechanics expert shows that the majority of the injury resulted from the second impact, a plaintiff may pursue additional claims or adjust damage calculations accordingly.

Methodological Rigor and Admissibility Concerns

To be effective, an expert’s theory of alternative causation must be more than speculative. Courts demand methodological rigor. The Daubert standard, which governs expert testimony in federal courts and many state jurisdictions, requires that an expert’s opinion be based on:

• Testable and tested hypotheses
• Peer-reviewed literature
• Known error rates
• General acceptance within the relevant scientific community

For example, in General Electric Co. v. Joiner (1997), the Supreme Court emphasized that a court may exclude expert testimony where there is too great an analytical gap between the data and the opinion offered. Alternative theories that do not meet these criteria will likely be excluded, weakening the overall case.

Therefore, attorneys must collaborate closely with experts from the outset to ensure that alternative causation theories are both credible and admissible. This may require independent research, modeling, or retrospective analysis, particularly in fields like epidemiology or mechanical engineering.

Expert Testimony as a Tool for Litigation Resilience

Alternative theories of causation are not merely tools for contesting liability—they are essential components of litigation resilience. A case built on a singular, untested narrative is vulnerable to challenge. By contrast, a case that engages multiple causation theories—each vetted through expert analysis—demonstrates a higher degree of preparedness and intellectual integrity.

This is particularly important in multidistrict litigation (MDL), where hundreds or thousands of claims hinge on generalized theories of harm. Courts overseeing MDLs often rely on bellwether trials to evaluate the strength of scientific evidence. Here, the ability of experts to propose and defend alternate causation theories can dramatically influence settlement posture, evidentiary rulings, and judicial perceptions of the case’s scientific foundation.

Conclusion

In complex civil litigation, causation is seldom linear. Medical complications, environmental exposures, mechanical failures, and behavioral outcomes are rarely the product of a single cause. Experts provide essential clarity by identifying and evaluating alternative theories of causation. Their work not only challenges unsubstantiated claims but also strengthens the evidentiary record, improves legal strategy, and enhances courtroom credibility. In a system where the burden of proof often hinges on scientific nuance, expert insight is indispensable.