An undertrial allegedly managed to escape from custody after his court hearing here following which three police personnel were arrested for dereliction of duty, an official said on Tuesday.Undertrial prisoner Supreet Singh alias Harry, lodged in Central Jail Amritsar, was brought to the court here for hearing in a criminal case yesterday, Senior Superintendent of Police (SSP) Batala, Inderbir Singh said.Harry managed to escape after the hearing, he said.