Before epilepsy was understood to be a neurological condition, people believed it was caused by the moon, or by phlegm in the brain. They condemned seizures as evidence of witchcraft or demonic possession, and killed or castrated sufferers to prevent them from passing tainted blood to a new generation.
Free will or not - if you have intentionally killed a bunch of people in the past it’s to be expected you’re likely to do it again. Such person shouldn’t be put to jail because we want to punish him. After all he could not have done otherwise. However as they’re danger to others something clearly needs to be done. They have to be separated from society in some way to prevent further harm but we should still treat them humanely and make sure their live is as good as it could be withing the circumstances.
If a bear wanders onto residential area we don’t shoot it because it’s evil. In my opinion the bear is no different from a murdered. They’re both slaves of their biology.