So we kill someone to show that killing someone is wrong

[DirkGently]

52. There's no good answer in a case like this.

My usual problem with the death penalty is that we do a notoriously terrible job of deciding who is guilty in horrific cases, and locking someone up at least allows for the possibility of a later correction to the injustice, which happens (fortunately or unfortunately) all the time.

What about a case like the Boston bombings, though? There is no question of guilt, or malice. There is no reasonable expectation of rehabilitation. Is it really that much more "just" or "compassionate" to lock up a 20-year-old boy / man for the next 60 years? To spend millions, keeping him alive without hope and subjecting him to all the miseries prison entails?

Maybe?

I don't know. I don't like executions either, but we're not clear as a civilization just what it is we're trying to accomplish when we catch someone like this. Rehabilitation of someone who maimed children and murdered strangers, then chuckled about "those people sure got cooked?" Permanent status as a caged, purposeless human being subject to any number of horrors -- including a reasonable possibility of being assaulted or murdered -- in prison?

He has to go away because we can't trust him to live among people. There's no good way to do that. Neither death nor prison is virtuous or merciful on our part. But we have to remove the threat he has proven himself to be.