Lefty Moriarty is a character in Dick Tracy. He was played by Lew Horn.
Moriarty was a uniform police officer in Dick Tracy's city. He observed Lips Manlis being abducted from the Club Ritz by agents of Big Boy, and he followed them to the South Side Warehouse.
Moriarty observed Big Boy threatening Lips, and he called in to police headquarters to report the activity. He was discovered and shot by Itchy.
Later, Chief Brandon mentioned the matter of a "grieving widow", indicated that Moriarty had not survived and that he had been married (since no other victims had been found at the crime scene).
"Lefty" was presumably a nickname.
Moriarty is a Irish surname that originally meant a title of "Master Navigator"
"Moriarty" is well-known in the annals of crime fiction as the surname of Sherlock Holmes' archenemy Professor Moriarty.