My colleague's admiration was short-lived. It evaporated when he realized that the experts’ change of heart had come only after they switched teams: Initially retained by the government, they were now in the employ of the defense.
Partisan bias is nothing new to legal observers, but formal research on its workings is in its infancy. Now, the researchers spearheading the exploration of this intriguing topic have put together a summary review of the empirical evidence they have developed over the course of the past decade. The review, by Daniel Murrie of the Institute of Law, Psychiatry and Public Policy at the University of Virginia and Marcus Boccaccini of Sam Houston State University, is forthcoming in the Annual Review of Law and Social Science.
Forensic psychologists’ growing reliance on structured assessment instruments gave Murrie and Boccaccini a way to systematically explore partisan bias. Because many forensic assessment tools boast excellent interrater reliability in the laboratory, the team could quantify the degradation of fidelity that occurs in real-world settings. And when scoring trends correlate systematically with which side the evaluator is testifying for, adversarial allegiance is a plausible culprit.
Systematic bias was also found in the scoring of two measures designed to predict future sexual offending, the popular Static-99 and the now-defunct Minnesota Sex Offender Screening Tool Revised (MnSOST-R).
One shortcoming of the team’s initial observational research was that it couldn’t eliminate the possibility that savvy attorneys preselected who were predisposed toward one side or the other. To test this possibility, two years ago the team designed a devious experimental study in which they recruited forensic psychologists and psychiatrists and randomly assigned them to either a prosecution or defense legal unit. To increase validity, the experts were even paid $400 a day for their services.
The research brought further bad tidings. Even when experts assign the same score on the relatively simple Static-99R instrument, they often present these scores in such a way as to exaggerate or downplay risk, depending on which side they are on. Specifically, prosecution-retained experts are far more likely to endorse use of "high-risk" norms that significantly elevate risk.
Several somewhat complimentary theories have been advanced to explain why adversarial allegiance occurs. Prominent forensic psychologist Stanley Brodsky has attributed it to the social psychological process of in-group allegiance. Forensic psychologists Tess Neal and Tom Grisso have favored a more cognitive explanation, positing heuristic biases such as the human tendency to favor confirmatory over disconfirmatory information. More cynically, others have attributed partisan bias to conscious machinations in the service of earning more money. Murrie and Boccaccini remain agnostic, saying that all of these factors could play a role, depending upon the evaluator and the situation.
One glimmer of hope is that the allegiance effect is not universal. The research team found that only some of the forensic experts they studied are swayed by which side retains them. Hopefully, the burgeoning interest in adversarial allegiance will lead to future research exploring not only the individual and situational factors that trigger bias, but also what keeps some experts from shading their opinions toward the retaining party.
Even better would be if the courts took an active interest in this problem of bias. Some Australian courts, for example, have introduced a method called "hot tubs" in which experts for all of the sides must come together and hash out their differences outside of court.
In the meantime, watch out if someone tries to recruit you at $400 a day to come and work for a newly formed legal unit. It might be another ruse, designed to see how you hold up to adversarial pressure.
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The article is: Adversarial Allegiance among Expert Witnesses, forthcoming from The Annual Review of Law and Social Science. To request it from the first author, click HERE.
Related blog posts:
- Remarkable experiment proves pull of adversarial allegiance (March 5 2013)
- Psychopathy: A Rorschach test for psychologists? (March 25, 2011)
- "Hot tubbing": Counterbalance for expert partisanship? (Aug. 11, 2008)