There are several fictional examples from books Agatha Christie’s “And Then There Were None” (not exactly, but close enough), television series (an episode of “Hardcastle and McCormick” which in recent rerun inspired this question :p), and movies (Star Chamber) of one or more judges going rogue and killing, or having someone else kill, convicted or suspected criminals who they perceive as having “escaped” justice in court.
Is there a real-life example of a judge, either sitting or retired, actually turning vigilante?
Yes, for a broad definition of “vigilante” that includes anyone without a badge or P.I. license “playing detective”. How much crime fiction would we be [del]spared[/del] deprived of if we didn’t have those?
Retired judge Hard[del]case[/del]castle was trying to catch the ones who he felt got away and put them in prison, not kill them outright. In the episode that prompted my question, the judges were killing “the ones that got away.”
Fair enough, not all vigilantes intend to kill their subjects. Intending to “merely” beat the crap out of someone or run them out of town is still vigilantism. On the other hand, I don’t think Nancy Drew or Ms. Marple, to use more fictional but non-judicial examples, would be considered vigilantes by most people simply because they have no official authority to be investigating crimes. They aren’t trying to take punishment into their own hands, just the solving of the crime(s). Hardcastle & McCormick is somewhere inbetween.
How much crime fiction would we be [del]spared[/del] deprived of if we didn’t have those? 
They aren’t trying to take punishment into their own hands, just the solving of the crime(s). Hardcastle & McCormick is somewhere inbetween.