A jury found 49-year-old Rodney R. Lloyd guilty Thursday of misconduct in public office. He was acquitted of a separate charge of abusing a prisoner.
Lloyd had arrested a man on a domestic-violence complaint last June and brought him to a police station. The criminal complaint says the man was taken into the booking room, where Lloyd slammed his head into a concrete wall.
His defense attorney, Steve Kohn, declined to comment after the hearing.
Lloyd faces a maximum penalty of 18 months in prison and a $10,000 fine when he's sentenced May 9.
Lloyd was fired after the incident. He's appealing that decision.