The Marcus-Nelson Murders (1973)

Based on a real-life case, Lieutenant Theo Kojack (Telly Savalas) leads an investigation into the murders of two women who were found in their Manhattan apartment. A young black man is arrested and confesses to the crime, but Kojack feels something is off about the case. Using his connections on the streets, he gets a tip from a drug addict about the real killer. Soon Kojack realizes that his department contains crooked cops, and that the accused man was forced into the confession.