First, the Roman Catholic Church does, in fact, sanction the authority of the state to execute criminals. Look it up in the Catechism, authored during JPII and issued with his imprimateur.
Pope John Paul II was personally spiritually opposed to the death penalty, but never EVER made such a statement as the policy or official doctrine of the Church.
Second...the commandment ,when properly translated, is thou shalt not "MURDER" ( not the word "kill" There is a strong moral distinction between "kill" and "murder"
Third..{Catholics need to get off their collective asses and stop executions. Too many American catholics that go to church and don't act on their faith in everyday life}... Catholics have a well founded fear of publicly espousing their religion. Remember JFK.. he had to publicly state and repeat that his aleigence was to the constution, and not his faith. The media in this coountry supports those catholics who embrace positions which agree with the liberal view of the democrat party, and any which seem to go anywhere away from the dogmatic left are smeared as "fundamentalists" or other such slanders.