Kellerman, Jonathan. An Alex Delaware novels

Originally published: New York : Random House, 2000

Someone has murdered euthanasia champion Dr. Eldon Mate - a self-styled Dr. Death responsible for scores of assisted suicides. In a burst of bloody irony, the killer chooses to dispatch the doctor in the back of his own suicide van, hooking Mate up to the killing apparatus dubbed the "humanitron"--And adding some butchering touches of his own. The case is assigned to veteran LAPD homicide detective Milo Sturgis, who turns, once again, to his friend Dr. Alex Delaware. But working this case raises a conflict of interest for Alex so profound that he can't even discuss it with Milo, and the tension that develops between cop and psychologist further complicates an already baffling and complex murder investigation