Law & Order (1990) : 16x15

After the body of a teenage boy is found dead in a warehouse, detectives use DNA to connect the boy to a convicted rapist and serial killer, then to the boy's mother, Allison Ashburn, the convict's ex-wife. While trying to solve Danny's murder, Fontana and Green learn that he recently got his girlfriend Tina pregnant, and his mother had seen him recently when she had given him money despite having claimed she hadn't seen him for months. Allison finally admits that she murdered her son after the police arrest her new husband John, but claims she did it to save the world from her son, whom she was convinced would become a monster just like her father. Borgia and McCoy face an uphill battle trying to convict the perfect soccer mom.