Few cases have had as profound an effect on the practice of expert testimony as the United States Supreme Court case of Daubert v. Merrell Dow , decided in 1993. This case is discussed elsewhere at length and will only be summarized here. The case held that trial court judges should be the "gatekeepers" of the admissibility of expert testimony, which had to meet the standards of reliability and relevance. Reliability, the more ambiguous standard, was to be determined be such tests as error rates, peer reviewed publication, widely accepted methodology and the like.1
The original Daubert case and its successors2,3 emerged, by their own internal descriptions, as attempts to end what was perceived as a significant influx of "junk science" into the courtroom. "Junk science" was envisioned as one expert's basing an opinion on flawed, factitious or idiosyncratic methodology that would not capture reliable approaches to the problem at bar. Indeed, a legal opinion used "necromancy," divination from corpses, as a metaphoric example of junk science. Courts mentioned in passing the need for a basis for an expert opinion that was more than an "ipse dixit"; that is, that the opinion was more than the fact that the expert "said so himself."
The Daubert decision may be seen as part of a larger concern both within the forensic field and within the larger society. Arguably, the trial of John Hinckley was a high water mark for public dissatisfaction with expert testimony, especially psychiatric testimony, though the testimony itself was reasonable and buttressed by clear bases. Since then, the media and the public appear to have learned some things or calmed down somewhat, so that strident media outcries about testimony are now relatively rare; this change may also reflect increasing sophistication in the forensic field itself.
Efforts by the American Medical Association to have expert witness testimony considered to constitute the practice of medicine represent another attempt to resist "junk testimony" from "carpetbagger" experts coming into a different state and attempting to define a standard of care that holds the local doctor to be negligent. If expert testimony is viewed as the practice of medicine (which it is not, on clinical, legal or ethical grounds4), it can then be effectively regulated through complaints to ethics committees and Boards of Registration.
The above measures may have as subtext the wish to exert some control over the "hired gun" phenomenon, a problem for the forensic fields which is notoriously difficult to control.5,6 Among the problems in resolving the hired gun issue are the challenge of definition (a hired gun sells testimony instead of time, but is this testimony sold?); proof (how can we be sure?); and distinguishing individual variance of standard or opinion from venality (is this opinion lying or merely outlying?).
From the viewpoint of the ethical expert witness the legal cases and ethical issues above place appropriate burdens on the witness to articulate carefully and thoughtfully the basis of the opinion being provided for the court. There are, however, two dimensions of the Daubert issue that have not been addressed in those opinions -- dimensions that may be relevant for the expert and thus worthy of discussion here. They are the true nature of problematic expert testimony and the basic issue of trust in the jury's capacities.
In actual forensic practice, excluding testimony that is the forensic equivalent of necromancy is not a useful remedial approach to the "hired gun" problem that bedevils our field. Testimony that is grossly deviant from general psychiatric practice is a rare occurrence; the usual form of venal testimony is a subtler thing. For example, consider a case of a young man who commits suicide by hanging himself in a hospital. The history and mental status revealed moderate depression but no suicidal ideation, intent or attempts in past or present, and no substance abuse; and he denied suicidal ideation or intent on direct inquiry; he was non-psychotic and had some future plans. Family history was negative for affective disorders, substance abuse or suicide.
An ethical expert testifies that the assessment and the plan - ward restriction with fifteen minute checks - are within the standard of care for that particular presentation. The presumed hired gun testifies that the patient should have been stripped, secluded and watched in constant observation, an approach which would have prevented the suicide.
Note how such testimony differs from a necromancy equivalent. Some patients are treated with the extreme measures described. Thus, while the extreme measures may be inappropriate or excessive for this case, they are still within the realm of clinical practice, albeit out at the edge. To cap the climax, although they would have been an infringement on rights and outside the standard of care, those measures might well have prevented this suicide. Consequently, the hired gun testimony here fits under the rubric of a "counsel of perfection" or a "you should have done more" opinion, both typical hired gun criteria that would not be screened out by Daubert challenge.
In sum, just as malpractice tribunals may work well to screen out ridiculous cases but not frivolous or meritless ones, so the various approaches - gatekeeper proceedings, defining testimony as medical care - may not suffice to screen out venal or misleading testimony.
Within the legal community, constituting judges, attorneys and law professors, another subtextual schism appears to exist, based on one's faith in whether the jury can itself winnow expert wheat from expert chaff when both are heard in court. This dilemma goes to the heart of the basis for considerations of admissibility of expert testimony.
Admissibility of evidence rests on a number of principles; these might include fairness to the parties, constitutional concerns, rules of evidence and the like. Of greatest relevance to our subject here is the balancing test between whether certain evidence will aid the jury in its deliberations or will be highly prejudicial to the case, e.g., by inflaming the jury's emotions. An example from a murder trial might be the issue of whether showing the jury evidence in the form of pictures of the mutilated corpse might inflame the jury into a rush to judgment, rather than permit them more coolly to decide the actual question before them, that is, whether this defendant in fact committed that heinous crime.
How does expert testimony fit into this balancing? An expert witness is defined in Federal Rule of Evidence 702 as someone who is "qualified as an expert by knowledge skill, experience, training or education" can aid the fact finder to "understand the evidence or to determine a fact at issue." The unexpressed converse of this model is the idea that a witness may foist off on the jury idiosyncratic, baseless or tendentious opinions, "cloaked in the mantle of expertise." In this model the expert is viewed as exerting a form of "undue influence" on the jury, whereby the jury is swayed from their common-sense rationality into giving inappropriate credence to the witness's claims.
Underlying this fear is a more basic concern about all expert witnesses. A school of thought within the legal community apparently sees every example of expert testimony as a potentially prejudicial intrusion on the sacred precincts of the jury's decision-making, as "invading the province of the fact-finder." For example, in one mock trial at an AAPL meeting the attorney for one side stated publicly that he retains an expert solely to cancel out the other side's expert, so that he can pitch his case to the jury's gut instincts. In the same vein, Harvard Law School Professor Arthur Miller has said in a televised debate on expert witnesses (infelicitously titled "Hired Guns"!) that the jury should be left to its own wisdom in evaluating evidence without any expert input at all, since the latter encroaches on the province of the jury's native judgment as representatives of the community.
The above dilemma can be portrayed as a basic dichotomy in the view of the jury as either suggestible and capable of being swayed by undue influence from a witness defined by the court as an expert; or as possessed of the common citizen's supposed canny ability to discern truth and to weed out non-credible testimony, even if issuing from a designated expert.
Daubert puts us as experts on our mettle to buttress our opinions. However, the hired gun problem remains alive and well. I have here tried to unpack subtextual issues in this problematic area. As always, the membership is invited to respond to this column.
1. Daubert v. Merrell Dow Pharmaceuticals 509 US 579 (1993)
2. General Electric Co. v. Joiner 522 US 136 (1997)
3. Kumho Tire v. Carmichael 119 S. Ct. 1167 (1999)
4. Strasburger LH, Gutheil TG, Brodsky A: On wearing two hats: role conflict in serving as both psychotherapist and expert witness. Am J Psychiatry 154:448-456, 1997.
5. Gutheil TG. The psychiatrist as expert witness. Washington DC: American Psychiatric Press, 1998.
6. Schultz-Ross RA. Ethics and the expert witness. Hosp Community Psychiatry 44:388-9, 1993.