well that was easy, there was 0 evidence against him and he got the death penalty looool

i think there's two key evidence against him:
1) he was literally 'caught in the act' (which was holding the knife that was still thrust into the body) by the most reliable witnesses: the police
2) his fingerprints are on the knife. assuming that it was the murder weapon and no other fingerprints were discovered there, it's pretty much 'decisive'.

and well, if you assume that he was basically wandering around prior to being discovered by the police, he had no solid alibi during the murder.

so yea, even if there was an investigation, the results might just be the same if the killer was really that thorough.