Mental illness is no defense, in reality, people with a mental disorder that predisposes them to being murderous, social misfits, are a burden to those who don't suffer from mental setbacks. Sure it's not "THEIR" fault that they're the way they are but it's nobody else's fault either. Why should "productive " elements of society have to be responsible for the safe keeping of a "non productive " element, an element that is a threat to the entire social component?? If you have a dog that impulsively bites do you keep the dog? Personally I'd shoot the fucking thing, and I have. Society wants animals and humans to enjoy equal status, that includes offing nuisance animals as well as humans. I didn't write the laws of nature so don't attack me.