If they can’t do that then they can’t do anything, they have video of the event which goes within inches of the unconscious body that is just out of frame, blood splatter etc. fills in the rest, that is why the jury convicted.
Evidently they did prove it. Now all of the bad guys are convicted or dead.
Given the situation the pharmacist found him in I would not consider him one of the bad guys. Especially when the other criminal gets released after 5 years at 19 because he was 14 at the time.