In my opinion, this should be done for almost anyone:

If they commit a minor crime, stealing,tresspassing, etc, they should go to jail for the first 2 times, and if they commit a 3rd one and end up in jail again then they are killed, because obviously, they aren't learning their lesson. Their first time in jail would be 2-5 years, the second time would be 10-15 years, and the third time would be death.

If they commit a Major crime, attempted murder, murder or mass murder, then they should serve 20 years, then be set free, if they kill again then that's death row for them.

Same thing for mass murderers, but the first time it would be 35-50 years depending on the amount that they killed