Expert witnesses play a vital role in court. In civil cases. Plaintiffs and defendants both rely upon expert witnesses to persuade jurors that a defendant was or was not liable for alleged wrongdoing. Experts also play a key role in helping jurors assess the damages that should be paid to a plaintiff when a defendant is liable for harm that the plaintiff suffered.
In criminal cases, defendants rely on experts to counter the testimony of crime lab employees. Defense experts also explain the psychology that underlies misidentifications, false confessions, and unreliable accusations.
In routine cases, the admissibility of expert testimony is uncontroversial. When drivers disagree about which car crossed the centerline to cause a head-on collision, there is little doubt that the court will allow both sides to call qualified accident reconstruction engineers to explain where on the road the accident probably occurred. The fact that experts have an honest disagreement has no bearing on the admissibility of their testimony, because resolving conflicts in the evidence is why we have juries.
In some cases, however, advocates for the insurance industry and corporate defendants have tried to portray expert witnesses as shills and hired guns — but only when they are hired by plaintiffs. Particularly in cases involving toxic torts, dangerous medical devices, and medical malpractice, advocates for defendants have long argued that experts who testify for plaintiffs should be kept out of the courtroom.
Complaints about “junk science” are sometimes legitimate, particularly when directed at the unfounded testimony that prosecutors have too often relied upon in criminal cases. Unfortunately, the term is primarily used by corporate and insurance company lawyers to disparage any expert testimony that helps suffering plaintiffs prove that their injuries were caused by corporate malfeasance.
Life Before Daubert
Until 1993, federal courts generally followed the Frye standard to determine whether expert evidence should be admitted at trial. The Frye standard allowed expert testimony to be admitted if it was relevant, if the expert was qualified, and if the expert’s conclusions were based on scientific principles and techniques that are generally accepted within the relevant scientific community.
Plaintiffs’ lawyers criticized the Frye standard because it prevented plaintiffs from relying on opinions based on scientific advances, no matter how sound those opinions might be, until the advances had come to be generally accepted by other scientists. Defendant’s lawyers, on the other hand, contended that generally accepted scientific principles and techniques can be manipulated to produce unsound results.
The Daubert decision addressed a claim that birth defects were caused by the anti-nausea drug Bendectin. The drug’s manufacturer, Merrill-Dow, relied on an expert witness who cited multiple studies purporting to show that Bendectin could be taken safely by pregnant mothers. The plaintiff relied on eight scientists who had conducted animal studies that found a link between Bendectin and birth defects.
The plaintiffs’ experts explained why the epidemiological analyses cited by the drug company’s expert were flawed. The trial court excluded the plaintiffs’ experts because their analysis of those epidemiological studies had not been peer reviewed and was therefore not generally accepted by the scientific community. The court also concluded that using animal studies to prove a link between a drug and a health condition in humans was not a generally accepted methodology.
The Supreme Court concluded that the Frye standard was too limiting because it prevents new or novel advances in science from being used as evidence until those advances are generally accepted. Parties should not be deprived of sound expert testimony simply because the field in general has not caught up with the advances made by expert witnesses.
On the other hand, the Supreme Court did not want to open the door to unsound testimony. It therefore devised a test that broadly admits expert evidence, whether or not it is generally accepted, provided that the expert opinion is based on the application of a reliable methodology to sufficient facts. The general acceptance of a methodology is relevant to that analysis, but it is not always decisive. A court might find, for example, that a testable theory with a known and acceptable error rate is reliable even if the scientific community in general has not yet embraced the theory.
In dissent, Chief Justice Rehnquist predicted that the new standard was unworkable because it would be applied by different judges in different ways. That criticism was prescient. Although the decision both broadens and narrows the range of expert testimony that should be deemed admissible, some judges view their “gatekeeping” job as shielding juries from any expert evidence unless the expert’s conclusions are indisputable, while other judges think it is the jury’s job to evaluate expert testimony if the jury could reasonably consider the testimony to be based on a reliable foundation.
Should the Daubert Rule Be Revised?
The essence of Daubert was eventually incorporated into Rule 702 of the Federal Rules of Evidence. Advocates for insurance companies and corporate defendants have urged states to adopt their own version of Daubert. They do so in the belief that empowering judges to limit expert testimony benefits corporate and medical defendants that are sued by injury victims and consumers.
Yet some critics contend that Rule 702 should again be amended because too many judges are allowing juries to do their jobs. The critics lament that the “unclear” standard created by Daubert is too often interpreted in ways that allow disputes about the reliability of expert testimony to be resolved by juries. They want courts to shield corporations from testimony that juries might find more reliable than a business-friendly judge.
For example, the general counsel for pharmaceutical giant Eli Lilly complains that “courts have written that the factual basis for an expert’s opinion is a matter for the jury to sort out, not the judge.” That’s hardly surprising. In the American system of justice, juries resolve factual disputes while judges determine the law. If there are competing views of the facts that underlie an expert’s opinion, the jury should decide which view of the facts is worthy of belief.
Eli Lilly’s lawyer also complains that some “courts have deliberately decided—as a matter of policy preference, not interpretation of the rule—to be more permissive with expert testimony than other circuits.” It would be more accurate to charge that some courts, as a matter of policy preference, have decided to be more restrictive than the Daubert decision permits.
As Georgetown Law Professor Lisa Heinzerling argues, Daubert was expressly intended to “open the courts to a wider range of admissible scientific evidence.” Judges who feel it is their duty to shield corporations from liability have used the decision as an excuse to prevent juries from deciding whether expert testimony is credible.
And as the late Professor Margaret Berger observed, widespread misunderstanding of the Daubert decision has resulted in “trial judges encroaching on the province of the jury to decide highly contested factual issues and to judge the overall credibility of expert witnesses and their scientific theories.” A cynic might think that those judges do not misunderstand Daubert so much as they misunderstand their duty to render neutral decisions, even when neutral decisions do not advance a corporate-friendly agenda.
Perhaps Rule 702 should be amended to make it clear that if any factual foundation for an expert’s opinion is reasonably supported by the evidence, whether an expert opinion is grounded in sufficient facts is for the jury to determine. Or perhaps it should be amended to reinforce the rule that an expert’s credibility is for the jury, not the judge, to determine. No other standard is true to the American belief that juries, not judges, resolve factual disputes in litigation.