Turkey's massacre of Amrenians in 1915 and the six year hunt and assassination of former Grand Visier Talaat Pasha as revealed in an internationally-covered Berlin murder trial in 1921.
When political assassins are caught and tried, they are almost always convicted. Soghomon Tehlina is the exception: This young Armenian is the only assassin ever to be found not guilty at his trial due to moral justification. Ironically, it is unlikely he would've been acquitted had the jury known the truth about two things: Tehlina had committed and gotten away with a previous assassination, and he was dispatched and funded on his mission by an Armenian organization located in Boston.
His target was Talaat Pasha, a leader of the Young Turk government of the Ottoman Empire before and during WWI. This book provides a detailed look at Tehlina's life and his trial, as well as the historical context, particularly the deaths of several hundred thousand Armenians in Turkey. After his 1921 acquittal in a Berlin courtroom, Tehlina married and moved to California, where he lived the rest of his life.