Our criminal justice system is based on the assumption of free will. If we believe someone has freely chosen ot commit criminal act, they must accept the consequences for their actions. 

The Catechism of the Catholic Church teaches that civil punishment for crimes must serve three principle purposes: 1) the preservation and protection of the common good of society, 2) the restoration of public order, and 3) the restoration or conversion of the offender. 
Our criminal justice system must protect the innocent, secure the public, and reform the offender. 

"Justice requires that to lawfully constituted authority there be given that respect and obedience which is its due; that the laws which are made shall be in wise conformity with the common good; and that, as a matter of conscience all men shall render obedience to these laws." - Pope Pius XI