>If a DA or their prosecutors could be trusted, we would not need to have jury trials.

I know you're quoting someone else, but that's beyond horseshit. It is a complete misunderstanding of trials. It is possible (indeed, common) to have an honest dispute of the facts of a case. That is the purpose of a jury: to be neutral, independent arbiters of facts. That is why civil suits (which usually do not involve the state as a litigant) also go to jury trial.