How would his lawyer have explained the shot under the chin???
Simply put, if the perp is dead, the police might have a *theory* about particular wounds, but it is exceptionally hard to propose a theory that rises to reasonable doubt.
The lawyer would never let the shooter testify, and outside of some very damning circumstantial evidence for which there is no plausible alternative, it is terribly hard to convict.
Remember that what the jurors hear is not what actually happened, but is often a blend of what the prosecutor says they think happened, according to police observation and forensic evidence; and the other story, what the defense argues *might* have happened. Importantly, the defense *does not* have to prove that there is guilt elsewhere, just that their client is not guilty of what the prosecution alleges, at least in the way he alleges it.
Police are just as prone as anybody to jump to conclusions about an event, after the fact. Sometimes they get it terribly wrong, but get emotionally invested in the wrong theory.
Unless the accused shoots his mouth off, even in damning circumstances, there is a good chance of acquittal.
The shooter in this case really fouled up in a whole bunch of different ways.