Please correct me if I get this wrong.   If the victim had been a woman and the stabber had been a man.  The man would likely accuse the woman of making him mad or, maybe swung a frying pan at his head.  You would know the man could be lying, as many others do in the same situation.

You would not prejudge the man or the woman until you had all the facts.  Correct?

In this case, it sounds like the police got to see and interview both people, hear their tone of voice, use past experience in domestic assault, etc.,  clues that none of us have available to us.    If you don't trust any police, then maybe you question the evidence.  On the flip side maybe the fool gave them lot's of reason to suspect him.  Drunk tends mess with good sense and the guy was drunk.

Either way, the accused is presumed to be innocent until proven otherwise in a court of law.      Our opinions don't mean squat to the court.