Hell Spawn: St. Tommy N.Y.P.D., Book 1 (Unabridged‪)‬

My name is Officer Thomas Nolan, and I am a saint. I can smell evil. I show mercy to the lesser criminals - the desperate. Even those I've put behind bars seem to like me. But now there's a serial killer bringing darkness beyond imagination to my city. I can smell his stench a mile away. But how can I prove it? How do you do forensics on a killer possessed by a demon?