You're asking about criteria. The judgement of the psych evaluator is what's taken as evidence in cases like this. It's primarily based on interview questions, so answering that you want to hurt someone is what's likely to get you locked up. I guess it's also based on actions, threatening or hurting someone else. That's also criminal territory however, and just as likely to wind up with you in jail as in a ward.

Why do you ask these questions, is wanting to hurt others something you struggle with? If so, I'm sorry to hear that; it must be awful.