To be honest, I have no idea how even family members can say with certainty that the howls are recordings of their own family members.
Those recordings are very poor quality. And howling is an unusual thing to be doing.
I think the judgement of the nearby witness is the most likely to be correct. He saw M apparently beating Z. And he thought Z was calling for help. He wasn't certain, but he gave his best judgement.
If I'm on the jury, I'm standing in his shoes. Watching.
And I am going to know that as the defendant, Z gets the benefit of the doubt.