His innocence was decided at the trial.
First problem: even though I've translated this sentence I still don't understand its meaning. Does it mean that the person was found innocent? Or does it mean that they debated his innocence at the trial and the outcome could still have been either innocent or guilty, and we just don't know the result?
Second problem: it seems strange to me to have a する verb for something that best translates in the passive. I'm used to the する/なる distinction where someone actively does something with する but things just happen by themselves with なる.
I've seen another example of a する verb being used passively recently (can't remember what it was now) so I assume it is quite common. Am I thinking about this in the wrong way can anyone shed some light on a better way to think about it?