Capital Punishment

 Pope Francis' encyclical, Fratelli Tutti, makes it perfectly clear that capital punishment is unnecessary. 

268. “The arguments against the death penalty are numerous and well-known. The Church has rightly called attention to several of these, such as the possibility of judicial error and the use made of such punishment by totalitarian and dictatorial regimes as a means of suppressing political dissidence or persecuting religious and cultural minorities, all victims whom the legislation of those regimes consider ‘delinquents’. All Christians and people of good will are today called to work not only for the abolition of the death penalty, legal or illegal, in all its forms, but also to work for the improvement of prison conditions, out of respect for the human dignity of persons deprived of their freedom. I would link this to life imprisonment… A life sentence is a secret death penalty”.

Just the fact that murder is still being committed proves that the threat of capital punishment doesn't prevent a murder from happening.  Even St. Augustine argued, 

 During the trial of the murderers of two priests, Saint Augustine asked the judge not to take the life of the assassins with this argument: “We do not object to your depriving these wicked men of the freedom to commit further crimes. Our desire is rather that justice be satisfied without the taking of their lives or the maiming of their bodies in any part. And, at the same time, that by the coercive measures provided by the law, they be turned from their irrational fury to the calmness of men of sound mind, and from their evil deeds to some useful employment. 

Putting perpetrators to work is a better idea than prison.  They could work and the money they make could go to the victim's family and the state.  Any idea would be better than killing people and/or locking them up for life.