body: (Just for reference, this question is for a story I'm working on, and I wanted a realistic look at the law's side of things.)
  
  
  So, a lot of fiction likes to play off the trope of a Vigilante. This person, (superhero or otherwise) often cuffs the baddies, and leaves them gift wrapped for the police, along with providing ***damning*** evidence to go with that. So my question is, does that actually ***help*** the police in any way?
  
  
  These situations are almost always portrayed as:
  
  
  * Acquiring evidence without a warrant
  * Falsely imprisoning a person/criminal (This does not always involve the Vigilante seeing the crime happen, but they are usually acting like a police officer and pre-empting the crime.
  * The Vigilante is generally unable to be present for the accused to 'face their accuser'.
  
  
  So, if evidence came from a known Vigilante, can it be used in a court of law?
  
  
  
title: Can a vigilante be useful for a police department?