Trial by jury; a pilot study of juror perception of mental health professional testimony in NGRI pleas for first degree international homicide.

The authors present a pilot statistical study of the way in which jurors perceived psychiatric/psychological expert testimony in ten court trials for first degree intentional homicide in which a plea of not guilty by reason of mental disease or defect had been entered. The reader is offered a short history of the insanity defense, of the trial by jury, and a discussion of the desired professional and personality prerequisites looked for in choosing a mental health expert. The study is based on a detailed protocol devised by two of the authors--a forensic psychiatrist and a psychologist--assessing various parameters of the professionality and demeanor of the experts on the basis of a statistically valid number of juror responses to the questionnaire. The results show that the jurors perceived the expert testimony as a useful, but not determinant factor when reaching their verdict. This is consonant with the definition of the rationale for using expert testimony as given by the Federal Rules of Evidence.