The forensic expert witness--an issue of competency.

Scientists submitting expert opinions within the legal system are expected to be knowledgeable in the forensic aspects of their particular science, as well as to be ethical and unbiased. Scientists are seldom able to decline a request to provide an expert opinion in their field, even when their forensic expertise is minimal. The competence of scientists providing expert opinions in forensic cases is reviewed here. Three examples of the perils of uninformed "expertise" in forensic biology, medicine and anthropology are presented.