Although pop culture often depicts the insanity plea as a common occurrence in the legal realm, it’s actually one of the rarest methods of defense. In order to prove an insanity plea, the defense must show that the killer did not realize what he or she was doing and also that they didn’t know the difference between right and wrong. Very few insanity pleas have worked in murder defenses and even fewer in the case of serial killers. Most serial killers who have pleaded insanity are unsuccessful in convincing a jury and are convicted regardless of their plea.
When there is mounting evidence against a serial killer, sometimes the insanity defense is the best way to try to stay off death row. This defense, however, ensures that the criminal must admit that they committed a crime, so a later not-guilty plea is difficult or impossible. Even in cases where a killer has been found not guilty by reason of insanity, serving time in a mental hospital is required. In some cases, like with Albert Fish, the jury may acknowledge the killer is insane, but find them guilty anyway.
Which serial killers have pleaded insanity? The serial killers on this list used insanity pleas to defend themselves in court.