Setting aside the JG case for a moment, in general your statement doesn't mean as much as you seem to think. Virtually all cases are resolved before trial. I don't want to look up the CA numbers again because these threads have a history of disappearing but I think the number in CA is around 98% of felony cases are disposed of before trial. And plenty of innocent people plead guilty. If you are sitting in jail because you can't make bail and/or you are offered x days if you plead guilty or risk 10X if you don't you may not want to wait it out and then roll the dice. And JG had the benefit that a very small fraction of people arrested have: the resources to put on a full throttle defense.