There is an upside to executing murderers. It's called justice. That's the biggest reason for capital punishment. Not being a deterrence. Having a murderer do 25 years or so and then get released is a spit in the face to justice. And it's no sign of "humanity."
Simple: they don't get out after 25 years. That's it. Let them rot in jail until they're collected away by the reaper. Getting raped, abused and eventually turning mad. Many consider this punishment worst than instant, soft, painless death.
