Young (defendant) saw an-eighteen-year-old boy being beaten by two middle-aged men on a sidewalk and decided to try to rescue the boy by attacking the middle-aged men. Young believed that the boy was being assaulted by the middle-aged men. The middle-aged men were undercover detectives attempting to arrest the boy for disorderly conduct. The boy was resisting this arrest. Young did not know that the middle-aged men were undercover detectives when he attempted to rescue the boy. Young was charged with assault, but the Appellate Division vacated the charge due to justification based on mistake of fact. The state appealed to the court of appeals.