As a former soldier I think a special unit should be formed specificly for certain crimminals. Most of these people are too deviant to take orders and be trusted with your life but, a special unit with discipline and training for covert activities may make these people have a different outlook on their behaviour and compassion for others.
Where have you and many others been hiding...there have always been, are now and especially in times of war, many armies have special units which are made up of 'criminals' that uses all their various talents. Some operate totally independently of any country and are for hire... They operate world wide are usually found in every conflict, usually on both or all sides...(hey, what the hell, it's all good money!

) The training differs dramatically though...some use real people for others learning how to kill...they use the terminally sick, mental patients, young and old that no one will miss and a new recruit so learns first hand the killing business so that when they really go into combat, they are already fully prepared with no drama over killing innocents, or bystanders...it's a tough world out there, wear a helmet.