Expert psychological testimony: Assisting or misleading the trier of fact?

Abstract

Abstract The consequences of psychologists' opinions are perhaps most strongly felt when offered in the context of a legal case. Due to this reality, courts are justifiably cautious when deciding whether to admit psychological testimony into evidence at trial. This commentary to the special section of Canadian Psychology on expert psychological testimony considers the circumstances under which expert psychological evidence ought to be deemed admissible. Drawing on the model of social analytic jurisprudence, guidelines are offered to psychologists for determining the propriety of their proposed testimony. As an undergraduate, one of us (Ogloff) conducted a research thesis in the area of eyewitness testimony. He was investigating whether hypnosis enhanced accurate eyewitness memory recall. During the course of the study, a family friend, a senior trial judge who later became Chief Justice of the Court of Queen's Bench in Alberta, took great interest in his work. Flattered, Ogloff took the opportunity to inform him of the details of the work as it progressed. Upon completion of the work, Ogloff was amazed at just how poorly the performed. With considerable excitement, he shared his concern about eyewitnesses with the judge. In turn, the judge asked him what legal reforms ought to be undertaken based on the thendeveloping body of eyewitness research. Being particularly naive about the legal system, Ogloff began to explain that psychologists should be involved in trials to inform judges and juries about the inherent limitations of eyewitness recall. For the first time in their discussions, Ogloff's excitement was met with stern resistance. The judge informed him that it was a judge's job to assess the extent to which an eyewitnesses' recall was - or was not - accurate. It was, the judge noted, a matter of common sense. It was clear that Ogloff had stepped on his judicial toes! The lesson taken from this anecdote has stayed with Ogloff and, in a very direct way, it speaks to the topic of the special section of Canadian Psychology on expert psychological testimony. In this article, we provide a brief overview of some of the issues concerning the admissibility of expert psychological opinion evidence. We discuss the role of expert testimony and outline the legal parameters of such evidence. Although we are sympathetic that there are cases where courts have incorrectly failed to admit psychological testimony into evidence at trial, we also highlight the opposite concern - that on occasion psychologists may overstate matters or otherwise mislead the courts. Drawing from the work of social analytic jurisprudence, we offer some general guidelines for psychologists and courts to help determine whether the expert psychological evidence being offered for admission into evidence at trial is sufficiently reliable and valid to assist the courts. Finally, we provide a brief introduction to this special section on expert psychological evidence. Psychology and the law share a common interest in understanding human behaviour (see Ogloff, 1992, 2000, in press; Ogloff & Finkelman, 1999). On occasion, courts actually require the evidence of psychologists - and other mental health professionals or social scientists - to help them make decisions. At trial, courts must resolve questions of law (e.g., whether some evidence is admissible, what is the interpretation of some aspect of a legal statute) and questions of fact (e.g., whether some event occurred, whether an accused intended to commit some act). Regardless of whether there is a jury, the judge is always the judge of the law and, as such, it is the judge who has the authority to resolve questions of law. By contrast, when there is a jury, it is the jury that is the trier of fact and, as such, it is the jury that is charged with resolving questions of fact. Of course, when the trial is being heard by a judge alone, the judge resolves both the legal and factual questions. …