they were the ones baby-sitting karyn's son, christopher, on the day of her murder. >> karyn had a tough time with her ex-in-laws. they're the ones who watched her son, and it was frequently stressful when she either would go to drop him off or to pick him up. >> but karyn's former husband, michael slover, had an alibi for the time of karyn's disappearance. >> he was working as a security guard at cub foods. he had made an arrest that afternoon at cub foods. the police had been there. >> since michael had an alibi, investigators turned their attention to karyn's current boyfriend, david swann. >> he'd had some run-ins with law enforcement. he had been put on probation in the past. he had pretended to be or impersonate a law enforcement officer in the past. he had spent time in a mental ward at a hospital. >> 34-year-old david swann had been dating karyn for only a short time. a background check revealed a disturbing incident. >> he had been involved in killing a deer and then had put the deer over a swimming pool and had used a chainsaw or like instrument to clean the deer. and due to th