You're absolutely right. But deterrence isn't the only issue of importance. We do want to select punishments that deter. But we also simply want to separate inc

You're absolutely right. But deterrence isn't the only issue of importance. We do want to select punishments that deter. But we also simply want to separate incorrigible offenders from society. Every year a murderer is locked up is a year they aren't killing anyone (except maybe other prisoners). I agree that increasing the probability of getting caught is good too, though.