> If all laws were prosecuted to the exact letter of the law we would not need juries. The DA will prosecute any case that they feel has enough evidence to secure a conviction, as this case had. It is the juries that determine if prosecution in each case is "just".

I think you're think of grand juries. They decide if there is enough evidence to go to trial, I.e. if the prosecution is just.

Even without grand juries, we'd still have juries that decide the verdicts. They decide if a conviction is just.