With no video, the defendant has a possible way out using 9.42. He says they guy tried to escape or threatened him. To convict, you need “beyond a reasonable doubt” that Section 9.42 does not apply.
He’ll have to base his defense on that. I don’t much like his chances, but it’s what the gangsters in Cali used to call a 13 1/2. 12 jurors, one judge, half a chance.