Article is poorly worded but the grandmother found the tainted milk. Doesn't specifically say if the police tested it and it was the concoction but I think it is likely.
Also as I've mentioned before on the board - either you want a theocracy or you don't. I personally don't - so what judiciary and our laws do should be independent as to what the Christian thing to do is.
I also am annoyed that people always are quick to blame mental illness for evil. Some people are just selfish assholes. That isn't a mental disorder that is just them being evil.