Members of law enforcement are supposed to take special care of juvenile and mentally challenged suspects such as Dassey. But on video, the detectives deviated from the Reid technique, giving him specific information he may not have known, telling him they already knew he was guilty and promising help if he confessed. Only police knew that Halbach had been shot in the head, Drizin said. If Dassey corroborated that evidence, they would know he was at the scene of the crime. The general questions, however, became more specific over time and the detectives finally asked him outright who shot her in the head. Dassey said his uncle had done it.