On February 27, 1859—in broad daylight—Congressman Daniel Sickles shot and killed Phillip Barton Key, U.S. Attorney for the District of Columbia and son of Francis Scott Key, composer of the “Star Spangled Banner.” Sickles suspected that Key was having an affair with Sickles’s wife. Criminal Court Judge Thomas Crawford instructed the jury on the defense of temporary insanity—that Sickles could not be held criminally responsible if, because of a mental impairment, he was incapable of governing himself in accordance with law or was unaware of the wrongfulness of his conduct, even if that impairment was only temporary.

The jury acquitted Sickles after 70 minutes of deliberation. It was the first successful use of a temporary insanity defense in American history. Sickles’s team of lawyers included Edwin Stanton, later President Lincoln’s Secretary of War during the Civil War.