Synonyms for Snitcher (same or very similar meaning)
WordNet sense 1 (a thief who steals without using violence):
pilferer, sneak thiefWordNet sense 2 (someone acting as an informer or decoy for the police):
canary, fink, sneaker, snitch, sneak, stoolie, stoolpigeon, stool pigeonFrom the ODE community, based on WordNetadd/edit