RT Journal Article SR Electronic T1 The Elusive Standard of Care JF Journal of the American Academy of Psychiatry and the Law Online JO J Am Acad Psychiatry Law FD American Academy of Psychiatry and the Law SP 358 OP 364 VO 45 IS 3 A1 Cooke, Brian K. A1 Worsham, Elizabeth A1 Reisfield, Gary M. YR 2017 UL http://jaapl.org/content/45/3/358.abstract AB In medical negligence cases, the forensic expert must explain to a trier of fact what a defendant physician should have done, or not done, in a specific set of circumstances and whether the physician's conduct constitutes a breach of duty. The parameters of the duty are delineated by the standard of care. Many facets of the standard of care have been well explored in the literature, but gaps remain in a complete understanding of this concept. We examine the standard of care, its origins, and who determines the prevailing standard, beginning with an overview of the historical roots of the standard of care and, using case law, tracing its evolution from the 19th century through the early 21st century. We then analyze the locality rule and consider local, state, and national standards of care. The locality rule requires a defendant physician to provide the same degree of skill and care that is required of a physician practicing in the same or similar community. This rule remains alive in some jurisdictions in the United States. Last, we address the relationship between the standard of care and clinical practice guidelines.