you get a public defender who essentially works for the prosecution

From DS9 Tribunal:

Ah, Mr. O'Brien, if it sounds immodest of me, I apologize, but the role of public conservator is key to the productive functioning of our courts. I'm here to help you concede the wisdom of the state. To prepare you to accept the inevitable with equanimity.

And that's exactly what's going on with these cases, with defendants being treated by their own defenders as if they are guilty and must be reeducated.

And just as in that episode, these "trials" aren't about justice. They're not even really about punishing the defendants. They're about intimidating anyone who might oppose them:

Whatever you've done, whatever the charges against you, none of that really matters in the long run. [...] This trial is to demonstrate the futility of behavior contrary to good order.