Daniel Murrie and his colleagues have produced a series of recent studies on “partisan allegiance” in forensic expert witness work (see citations below). They define partisan allegiance as the tendency for experts to bias their testimony in favor of the side that calls them. They demonstrate this through ingenious experiments with PCL-R ratings. The response in the legal and professional psychology communities has been phenomenal.
Karen Franklin has commented on this issue in detail at her forensic blog: http://forensicpsychologist.blogspot.com/2013/03/remarkable-experiment-proves-pull-of.html
In several of the pieces, Murrie et al remind readers that there are ethical implications for expert testimony. These ethical implications are not merely best practice guidelines for practitioners, which is surely a positive thing, but may also create ethical accountability, even liability for the expert witness work they do. Ordinarily, we might expect differences in opinion, the so-called “battle of the experts,” but ethical mandates for objectivity,valid methodology,and notice of limitations are clearly worded in the APA Ethical Principles for Psychologists and Specialty Guidelines for Forensic Psychology.
Ordinarily, we would rely on rules of evidence and judges to make determinations about what sort of science they will admit as evidence in their court rooms, but it well know that standards vary widely, and judges may be prone to admit shaky evidence, but allow the jury to consider the weight.
The idea that expert witnesses in forensic cases may have to answer for their partisan allegiance to a state or national ethics committee should serve as a warning to comply expert testimony with the following non-exhaustive list of standards:
APA Ethics Code-2.04. Bases for Scientific and Professional Judgments. Psychologists’ work is based upon established scientific and professional knowledge of the discipline.
APA Ethics Code- 9.01. Bases for Assessments. Psychologists base the opinions contained in their recommendations, reports, and diagnostic or evaluative statements, including forensic testimony, on information and techniques sufficient to substantiate their findings.
Forensic Specialty Guidelines 4.05. Knowledge of the Scientific Foundation for Opinions and Testimony. When providing opinions and testimony that are based on novel or emerging principles and methods forensic practitioners, when possible, make known the limitations of these principles and methods.
Forensic Specialty Guidelines. Forensic practitioners seek to provide opinions and testimony that are sufficiently based upon adequate scientific foundation,and reliable and valid principles and methods that have been applied appropriately to the facts of the case.
Karen Franklin notes that experts have an ethical duty in the quality of their forensic work, to know the know the relevant literature and controversies, acknowledge scientific limitations, and understand the potential harms.
I will have more to say about bias in forensic testimony in following blog posts.
Bocaccini, M et al (2013, December 16). Evaluator Differences in Psychopathy Checklist-Revised Factor and Facet Scores. Law and Human Behavior (re-publication online version).
Murrie, DC (2008). Does Interrater (Dis)agreement on Psychopathy Checklist Scores in Sexually Violent Predator Trials Suggest Partisan Allegiance in Forensic Evaluations? Law and Human Behavior, 32, 352-362.
Murrie, DC (2009). Rater (dis)agreement on risk assessment measures in sexually violent predator proceedings: Evidence of Adversarial Allegiance in Forensic Evaluation? Psychology Public Policy & Law, 15, 1, 19-53.