The article itself didn’t do a good job of explaining, but judges can punish the prosecution for false arrests. There are several issues.

The state claims he wasn’t detained, he voluntarily presented a fake ID, and then they arrested him for that. Later they held him for murder. That’s their claim… The defense is saying no, they detained him first (i.e., for murder), and he unwillingly gave them a fake ID and spoke to them.

One possible outcome: The judge sides with the prosecution that he wasn’t detained at first.

Another possible outcome: The judge sides with the defense and says that the prosecution needs to justify the initial detention, because the fake ID happened later. Then presumably the prosecution says that the cops were arresting him for murder. If they had probable cause or an arrest warrant, they could do that. So they’ll have to show evidence of that in court. If they can’t, then probably anything he said will be thrown out (no Miranda) and any evidence seized from his backpack will be inadmissible in any court case (unlawful search and seizure). Even if they can, then anything he said will still be thrown out (no Miranda).

There are some less likely outcomes as well, if somehow the defense could show that the pigs were acting with malice or something, but based on what we’ve seen so far, let’s suppose one of the above is what usually happens in situations like this. And usually the judge sides with the prosecutors.