If a defense computer works then it should be able to argue against a prosecutor computer, and the two decide the human’s fate.
Computers could also use their vast knowledge and records to decide which nations should be at war with each other, how the war would proceed, and what the result would be, then they could just zap the appropriate percentage of humans in those populations and appropriate infrastructure, and the war would be done without us ever having to leave our living rooms.
There was a Star Trek Original Series episode about that very idea.........