This article, in memory of Bernard Diamond, revisits his seminal editorial on the "Fallacy of the Impartial Expert." In a later article he formulated his thesis most succinctly: "There is no such thing as an impartial expert witness; the objectivity of the expert witness is largely a myth." I argue that the implications of his challenging assertion have as yet not been fully recognized. Ultimately, they also invite a revision of the American Academy of Psychiatry and Law's Guidelines for the Practice of Forensic Psychiatry. The Guidelines should emphasize more than they do experts' commitment to honesty and to informing fact finders about the extent and limits of their scientific knowledge, the facts on which their opinions are based, as well as the scientific and value assumptions that underlie their testimony.