Argument: The Catholic Church has long opposed the death penalty
"A Culture of Life and the Death Penalty, A Statement of the United States Conference of Catholic Bishops Calling for an End to the Death Penalty". 2005. - While complex, the teaching of the Universal Church is clear. It has developed over time and has been taught most powerfully in the words and witness of Pope John Paul II. Catholic teaching on the death penalty is clearly articulated in the encyclical The Gospel of Life, the Catechism of the Catholic Church, and the Compendium of the Social Doctrine of the Church. In Catholic teaching the state has the recourse to impose the death penalty upon criminals convicted of heinous crimes if this ultimate sanction is the only available means to protect society from a grave threat to human life. However, this right should not be exercised when other ways are available to punish criminals and to protect society that are more respectful of human life (ie. life without parole).
Catholic New Servic. "Church opposes abortion, death penalty -- but experts see difference". 2004 - Regarding capital punishment, [the Catholic Church] says that in today's world 'the cases in which the execution of the offender is an absolute necessity 'are very rare, if not practically nonexistent.' The quote within the quote is from Pope John Paul II's 1995 encyclical, 'The Gospel of Life'. Both teachings originated early in church history, with opposition to capital punishment growing stronger in the 1990s under the current pope, said Dominican Father Kevin O'Rourke, bioethics professor at Loyola University in Chicago. 'Pope John Paul II has developed it more firmly to where it is almost never justified,' he said.
Washington State Catholic Conference, "A Call for the Abolition of the Death Penalty", 2005 - Even in the fifth century, teachers like St. Augustine cautioned that executions were a last resort saying, '…our desire is rather that justice be satisfied without the taking of lives.'