You might even call them Killers Without Conscience.
I never, for a moment, ever believed they HAD consciences.
How could anyone who justifies murdering infants, murdering the elderly, stealing from one person to bribe another, etc., etc., HAVE a conscience?
What they believe in, and how they live their lives precludes having anything remotely resembling a moral base or conscience.
We need to remember that when dealing with them - and deal with them at that same level if the time comes.