I just don't get how he thought this logically, holding onto the matching murder weapon in his home (not even attempting to throw it in a lake or woods in his multi-hour drive home) and being in possession of the car, using his car and plates in a city with cameras on every street (remember the ONLY probably cause in the arrest affidavit was his car, that he was in possession of it, and that it was on camera near the scene of the crime that night). That's basic TV crime drama stuff, and for realistic reasons. Leaving the spent casings sure, maybe he doesn't reload like me and he's not used to picking up his brass, but the two huge things (dispose of murder weapon, don't use own car/plates) could have easily been avoided, even by an amateur. I mean he couldn't have stolen some plates or masked them but he's willing to leave the murder weapon at home and have a class 3 felony suppressor in Cook County, IL?? I am very curious how "sloppy" the rest of the crime scene was and just how there wasn't more definitive surveillance footage (perhaps there was).
These things led me to speculate he was not consistently of sound mind, but just enough "there" in his rage or psychosis for a rushed premeditation (or maybe your point about substance abuse which may very well be a variable). Maybe he was savant smart in medicine, and just common sense dumb. I think he got lucky in many aspects; lax security by my standards, type of neighborhood that wasn't too nosy , city living desensitizes one to noises and activity, residential cameras and alarms that were more style over substance. etc.
Prisons are full of people who thought they would not get caught.
And some of them are smart and educated.
But yes why would an intelligent, well educated, medical professional commit a horrendous double murder, but not hide the evidence of the crime?
I think most lay people have a hard time wrapping their heads around the criminal mind or seemingly normal people who go completely off the rails and do unspeakable things. But the courts, defense attorneys, the mental health professionals are used to working with a population committing crimes and who think, feel, act in abnormal ways.
In terms of what might be going on in this killer's head:
Sometimes people are grandiose and overly confident, like in the case of narcissists. They are used to being the smartest person in the room, and are good at fooling people. They assume everyone else is stupid. They are the star of the show and others are just expendable props. Sometimes when these people are interviewed, they don't even come up with good lies to cover up the crime, or hide evidence. They think you will buy what they are selling, no questions asked. They see themselves as special and the rules don't apply to them. The may harbor grievances real and imagined.
Yes this man could be smart in one area of life, but clueless about everything else. Lack of social skills, judgement, logical thinking. Also if he spent most of his adult life in pursuit academic and clinical goals, he may not have watched or read police procedurals, cop shows, etc.
If he abused drugs and booze, all of this would be ramped up signficalty.