Philip Barton Key II (April 5, 1818 – February 27, 1859)[1] was an American lawyer who served as U.S. Attorney for the District of Columbia.

[1] Allegedly the most handsome man in Washington[6] and by 1859 a widower with four children, Key was known to be flirtatious with many women.

[2] Dan Sickles, though a serial adulterer himself, had accused his much-younger wife of adultery several times during their five-year marriage, and she had repeatedly denied it to his satisfaction.

[4] But then Sickles received a poison pen letter[13] informing him of his wife's affair with Key.

[18] Sickles was acquitted based on temporary insanity, a crime of passion, in one of the most controversial trials of the 19th century.