Ok, that timeline that prosecutor just mentioned doesn't make sense. He wouldn't have given her the drugs and immediately held her head under water -- he would have had to wait some time for the drugs to take effect.
ETA: More likely between 10:00 - 11:00 he gave the drugs, then went to office to get his picture taken, went back home to drown her, then picked up Ada
He presented a pretty long window of opportunity. Over an hour.