he gave debbie poison. she developed gastric symptoms. nvince her doctors to perform gallbladder surgery that she wouldn't survive. had debbie died during surgery, tony could argue, as he did in sarah smith's case, that people occasionally die in surgery and that he shouldn't have been singled out. >> and in tony's eyes, that would have vindicated him. see, my own wife died under a doctor's care in a hospital while having surgery, and that's what we felt was his prime motivation. >> but why didn't she die from the massive dose of arsenic? medical experts say this was miscalculation. when tony gave his wife smaller doses of poison, she developed a tolerance for it, so the higher doses later had less of an effect. >> i'm sure he was thinking, i can't believe she's still alive. i can't believe i gave her so much and she's still here. i think he just got panicky, and it wasn't working, so i think that's when he just figured, i'm just going to give her a massive dose and be over with. >> apparently, his daughter's ingestion of the arsenic was u