@YAMystery Because it's the water that's poisonous, not the pill? It doesn't say anything about the killer taking the pill specifically with water as with the victim, and since the pills are identical, the killer can't know the difference. Besides, if they were identical, they would both be poisonous, right? My guess is that the water is poisonous, not the pill. They're both safe pills, ergo it doesn't matter which one he takes, as long as it's not with the same water, or any water, as the victim.