One of the reasons given by the capital punishment abolitionist movement—and even noted in the Catechism—is that current penal technology keeps prisoners from threatening society so effectively, that capital punishment is no longer needed to protect the innocent from the aggressor.
The Catechism says:
“2267 Assuming that the guilty party's identity and responsibility have been fully determined, the traditional teaching of the Church does not exclude recourse to the death penalty, if this is the only possible way of effectively defending human lives against the unjust aggressor.
“If, however, non-lethal means are sufficient to defend and protect people's safety from the aggressor, authority will limit itself to such means, as these are more in keeping with the concrete conditions of the common good and more in conformity to the dignity of the human person.
“Today, in fact, as a consequence of the possibilities which the state has for effectively preventing crime, by rendering one who has committed an offense incapable of doing harm - without definitely taking away from him the possibility of redeeming himself - the cases in which the execution of the offender is an absolute necessity "are very rare, if not practically nonexistent."
This story from the Cleveland Plain Dealer is but another in a long line of articles noting the complete opposite.
“Dimorio McDowell transformed his prison cell into a business office with nothing but a mobile phone and a lot of chutzpa.
“From 7 a.m. until midnight, seven days a week, McDowell worked tirelessly building a Cleveland criminal enterprise that did up to $1 million worth of work.
“Want a jumbo flat-screen, but don't have $2,000?
“McDowell and his unsavory team of Cleveland shoppers could fetch a 55-inch TV and anything else you wanted -- stainless steel refrigerator, hardwood flooring, laptop computer -- for half the store price.
“Just give them a few days. McDowell was serving time for credit card fraud at Fort Dix federal prison in New Jersey. But one of his associates would meet you at a Cleveland gas station with the loot.
“Incarceration in the largest U.S. prison was doing nothing to slow down McDowell's life of crime. Then, in October 2009, McDowell accidentally tripped across the path of a small-town Summit County cop.”