By Carl E. Fisher, David L. Faigman, & Paul S. Appelbaum
UC Hastings Research Paper No. 110
August 17, 2014
Psychiatry is an applied science. It thus shares the characteristic of all applied science in that it is ultimately applied at two levels – general and specific. Scientific research inevitably focuses on aggregate data and seeks to generalize findings across persons, places or things. However, in the courtroom, as is true in other applied settings, the focus is usually on an individual case. Thus, psychiatry presents the challenge inherent in all scientific evidence of reasoning from group data to an individual case, which is termed the “G2i problem.” But psychiatry, unlike many scientific fields that come to court, also confronts the G2i problem in its daily practice, since mental health professionals routinely diagnose and treat individuals based on aggregate data. Yet approaches to the G2i problem in clinical psychiatry do not necessarily fully align, or fit, the uses to which it is put in the courtroom.
In this Article, we employ the G2i lens to examine the admissibility of psychiatric expert testimony, both as regards general research findings – or “framework evidence” – and the application of those general findings to specific cases – or “diagnostic evidence.” Although the rules of evidence that apply to G and to i are the same, the scientific and professional considerations that must be evaluated in regard to each are fundamentally different. G2i inference provides a useful lens by which the interactions of psychiatry and law can be better understood and managed.