The State and society lose out hugely. Nothing is gained and much is lost on a moral\ethical\financial level. An execution is State sanctioned Homicide. It's literally what the cause of death is recorded as in places such as Texas. The person is killed in a premeditated manner years after the offense. It's been proven to not give any reasonable deterrent to murders. They have been in prison for years, and while in prison pose no threat to society. Society isn't made safer. You're killing them for no gain.

Capital punishment is a statement that the State is prepared to kill someone. You've described the men as "evil". How does murdering them make Society any better? In terms of justice you can focus on punishment or rehabilitation as the main goal. Rehabilitation is better as it gets better results but also results in the criminal acknowledging their wrong doings. Death is a huge punishment. No one learns from it though. You spend millions of dollars killing someone when prison has the same exact advantages without the death. There's rehabilitation. Some of these men go to their deaths rehabilitated and some don't. Those who don't who aren't innocent may be "evil", but your killing them does achieve anything but perhaps satisfy some primal blood lust as they 'deserved it'. It's a statement of the State giving up on rehabilitation. I don't think the state should do that. The state isn't meant to take the easy way out. To give up on the goal on rehabilitation is disgraceful. The States goal should be to get these people to feel remorse for what they've done. The best result for the victims survivors is a heart felt apology.