A guy tried to assassinate FDR and accidentally or maybe on purpose hit the Mayor of Miami instead, they tried him and executed him only a week or so after the Mayor died.
Giuseppe Zangara (September 7, 1900 – March 20, 1933) was the assassin of Chicago mayor Anton Cermak, though United States President–elect Franklin D. Roosevelt may have been his intended target.[1] Roosevelt escaped injury, but five people were shot including Cermak.
http://en.wikipedia.org/wiki/Giuseppe_Zangara#Assassination_attempt
Crime on February 15th, execution on March 20th. No-one denied him his right to a speedy trial.
Leon Czolgosz:
Sept. 6, 1901: shot President McKinley
Sept. 14, 1901: President McKinley dies of his wounds
Sept. 23, 1901: Czolgosz trial begins; he is found guilty 8 hours, 23 minutes later.
Oct. 29, 1901: Czolgosz executed by electrocution
Justice administered speedily, and without delay.