I remember a time, way back, when if a criminal with a rap sheet swallowed a lethal dose of fentanyl and then croaked on the street, that was considered the primary cause of death and the arresting officer wasn't charged with murder.
The point being, the justice system has become all sorts of fucked since the old days when the principle was "need solid evidence for conviction"
And I'm not saying the dude didn't do it, I'd be willing to bet physical cash he did do it, and I wouldn't bet on it but from what I've seen I feel like he's probably too stupid to effectively clean up a crime scene. But these days "physical evidence" doesn't matter near as much as "convince the jury full of facebook moms"