Maybe I made it sound more complicated than it really is. It’s actually pretty simple and informal; and as I said, fairly quick–I bill Legal Aid, but it’s at Legal Aid’s rate and never for more than two hours.
On to your question. Even though they are detained in jail, inmates retain certain constitutional rights–for example, they always have the constitutional right to speak with and instruct a lawyer. They also have the right not to be forced to incriminate themselves in these proceedings–and my presence helps to remind any guards present that they may not ask questions that would result in self-incrimination.
But I think there is more to it than just that. It’s an educated guess, but I would think one reason that the system is in place to ensure fair treatment for all. The inmates have many complaints, but one thing they cannot complain about under this system is that they have no say in disciplinary proceedings that affect the few privileges they have. They have a say, and if they wish me to say it for them, I will. If they want advice on their rights, I’ll give it. To an inmate with questions or concerns about his rights or the proceedings, I’m pretty much the only person whom they can trust to give them the straight dope and to be on their side. For obvious reasons, they don’t always trust the guards to be neutral.