Corrected entry: Scorpio is not charged with any crime due to inadmissible evidence. There is no reason why he could not have been charged with assault on a police officer, and with shoot to kill a police officer, given he assaulted Harry and shot Chico, who both were witnesses.
mightymick
15th Feb 2011
Correction: Everything about that night is tainted evidence and therefore not admissible, but not only that, the DA wasn't willing to try to prosecute on any crime because of Harry's actions.
Bishop73
Scorpio's face was covered with a ski mask so Harry or Chico couldn't identify him for assaulting or shooting a police officer. I did find a 1997 constitutional law paper from the University of Chicago (Dirty Harry and the Real Constitution, Michael Stokes Paulsen) that argues Scorpio could be tried and convicted.