Liston's criminal record, compounded by a personal association with a notorious labor racketeer, led to the police's stopping him on sight, and he began to avoid main streets. On May 5, 1956, a policeman confronted Liston and a friend about a cab parked near Liston's home. Liston assaulted the officer, breaking his knee and gashing his face. He also took his gun. He claimed the officer used racial slurs. A widely publicized account of Liston resisting arrest—even after nightsticks were allegedly broken over his skull—added to the public perception of him as a nightmarish "monster" impervious to physical punishment. He was paroled after serving six months of a nine-month sentence, but prohibited from boxing during 1957. After repeated overnight detention by the St. Louis police and a thinly veiled threat to his life, Liston left for Philadelphia, Pennsylvania.