On April 26, 1859, legal history was made when Dan Sickles used the “temporary insanity” defense for the first time in history as a defense against murder. It was the details of the case, however, that were truly insane.

To start with, the killer (Dan Sickles) was a member of Congress, the victim (Philip Barton Key) was the U.S. Attorney for the Washington District, and the killing happened right across the street from the White House. Furthermore, the killer and victim had been close friends. The reason for the killing is that Sickles had recently found out that his wife was having an affair with Key and, as he confronted his wife, saw Key outside trying to get his wife’s attention.

Sickles was represented by a team of 8 high-powered, famous lawyers. The prosecution never had a chance. Despite the fact that Sickles himself had been having an affair for years, and was well known for having a violent temper, and had demonstrated premeditation by stopping to arm himself with three guns before going after Keys, the defense team argued that he was so hurt and outraged by the affair that he went temporarily insane, driven into a frenzy, and didn’t know what he was doing. It also managed to make the trial all about Keys and his supposed moral shortcomings. By the time the trial was over, newspapers were thanking Sickles for “saving all the ladies of Washington from this rogue named Key.” The jury found him not guilty.