Peter

It seems realistic to me, but my knowledge of the legal system, wrt matters of this sort, is based more on TV than experience, so judge of that what you will :)

The reason I chose 'no' to the question about it being just is that Bob had a strategy, admitting to the crime he didn't commit in part to maintain his standing in the criminal underworld. Also, he deliberately prevented his friend from being arrested for a crime he committed (which might have been the result of further investigation if he had not confessed, even if he had not said 'My friend did it'), which is in itself a crime that he hasn't been put on trial for.

But as you can see, all my quibbles are about justness, not about knowledge, so I should stop there :)