What I suggest is a passport scheme where accredited counter espionage agents have to decide if the person is a dangerous TYPE of human ie - if it looks like a maniac then it probably is an maniac. Such a person would have to be castrated (if a male) and either relocated to a distant land or incarcerated for life.
This would make such peoples unwelcome and would disappear from our streets.
This would make such peoples unwelcome and would disappear from our streets.