What Is an Environmental Expert? the Impact of Daubert, Joiner and Kumho Tire on the Admissibility of Scientific Expert Evidence
Gagen, Andrew B., UCLA Journal of Environmental Law & Policy
Environmental experts are typically environmental engineers and environmental and occupational health doctors (1) whose testimony is based on "scientific, technical, or other specialized knowledge" that "will assist the trier of fact." (2) In complex environmental and toxic tort (3) cases, "scientific, technical or other specialized" expert evidence (4) "has become virtually indispensable, especially on the issues of causation (5) and damages." (6) For the following reasons, environmental and toxic tort expert evidence must be treated differently than ordinary evidence in environmental and toxic tort litigation.
First, unlike expert evidence, ordinary evidence is typically derived from fact witnesses whose testimony is limited to inferences and opinions based on firsthand knowledge. (7) An expert witness' testimony, in contrast, is not limited to firsthand knowledge or observation. (8) Scientific expert witnesses may testify to inferences and opinions based on data (tests, models, and peer publications) "reasonably relied upon by experts in the particular field." (9) A distinction is recognized between lay and expert witnesses because experts possess an "unique ability" to draw conclusions from data. (10) The United States Court of Appeals for the District of Columbia first recognized this distinction in Frye v. United States. (11) Congress codified this distinction in the adoption of Article VII of the Federal Rules of Evidence ("Rules") in 1975, (12) which separates Rule 701 (13) from Rules 702 (14) and 703, (15) in order to distinguish ordinary witnesses from expert witnesses. Since the enactment of the Rules, the Supreme Court has twice recognized that Rules 702 and 703 grant expert witnesses "wide latitude to offer opinions ... not based on firsthand knowledge or observation." (16) Because expert witnesses are not limited to firsthand knowledge, their testimony ought to be treated differently than more reliable firsthand evidence from lay witnesses.
Second, expert evidence in environmental and toxic tort cases often "involve[s] complex scientific theories that are novel, and affect many people beyond just the individual litigants." (17) Novel scientific expert evidence is evidence that has not received widespread peer review (18) and/or acceptance from the judicial or scientific communities. (19) Such evidence raises countervailing concerns. On the one hand, a "liberal admission standard [may] impede the judicial process" (20) by allowing "junk science" (21) into the courtroom. On the other hand, "a restrictive standard will prevent courts from becoming fully informed about [novel] scientific developments," (22) which may be relied upon by toxic tort and environmental litigants. As technology and the underlying scientific theories continue to grow, more litigation will include complex and/or novel scientific expert evidence. (23) Given the possible increased reliance on novel scientific evidence and the potential impacts of such litigation beyond just the individual litigants, (24) scientific expert evidence ought to be treated differently than ordinary witness testimony.
The third reason for treating scientific expert evidence differently than lay witness evidence in environmental and toxic tort litigation is the latency period of the diseases involved in such litigation. (25) A disease may develop many years after an acute exposure or after many years of long-term, low-dose exposure to a carcinogen or toxin. (26) The long latency period obscures the chain of causation. The causation chain is further obscured in novel cases because the mechanism by which the toxin causes the disease may not be understood. (27) Subsequently, a fact witness, or a witness with firsthand knowledge, does not typically possess the experience or knowledge to explain the causal link to the trier of fact. (28) Given the technical and complex nature of proving causation in a typical toxic tort claim, (29) scientific expert evidence is needed to establish a prima facie case. …