I don’t think you read the comment you are replying to:

If necessary, they should be removed from society and locked up, if they pose a danger to others.
Putting them in a typical American prison that is designed to make their life as miserable as possible while extracting free labor helps neither them, nor the victims, nor society.

Depends on the crime, the motive and their state of sanity.
Generally, it’s for a court to decide.