Yeah - after I had a Judgement available, before I took the seat I went down to the cells. I'd found the cells previously, and wondered if maybe interaction was available with the prisoner to gain more insight into them, or inform my choice, etc. I was surprised when the cells were empty, even when you had a prisoner awaiting judgement. Where are they being held before you judge them...?
Total WAG with no inside information to back it up: this seems like a candidate for content that didn't make it in before the deadline. I can see Bioware not wanting to simply have a figure standing there you couldn't interact with, that would be more misleading that atmospheric. There's my prisoner, I'm the Inquisitor, I can't even talk to him? Any interaction would have required more VA recording, dialogue being written, etc. So if that was planned, but didn't make it in before release, better to cut the whole thing and not have anyone in there. It would be very wrong to have a prisoner be scenery you couldn't interact with in any game; so much more so from Bioware.