In 1859, a Murderous Congressman Pioneered the Insanity Defense

After gunning down his wife's lover in broad daylight, Daniel Sickles tried to escape the gallows by claiming he was out of his mind.

Illustrations by Vinnie Neuberg

“Temporary insanity” is a relatively modern invention. The question of insanity in criminal cases became part of American law in the course of two 19th-century murder trials, each involving a hotheaded protagonist, a lover’s tiff, and a killing in broad daylight. Together, these trials set the tone for temporary insanity jurisprudence and showed that in American law and society, insanity is a gendered condition.