In one episode of the TV show Sherlock, Holmes and a prisoner has a conversation where Holmes corrected him grammatically many times. The following is just part of that.
Prisoner: (annoyed) Did it! STABBED HER! Over, and over, and over, and I looked down and she weren't… (Sherlock just sighs) …wasn't… moving no more… (Sherlock rolls his eyes) …anymore. (calmer) God help me, I don't know how it happened, it was an accident, I swear! (Sherlock gets up to leave) Hey, you gotta help me, Mr. Holmes! Everyone says you're the best. Without you… I'll get hung for this.
Sherlock: No, no, Mr. Bewick, not at all. (beat) Hanged, yes.
According to Cambridge Dictionary, both "hung" and "hanged" could be the participle form of "hang"
Why Sherlock insists "hanged" there?