I'm fascinated by the case of Bradley Birkenfeld, the former UBS banker who helped rich people avoid taxes by stashing their money offshore.

Birkenfeld blew the whistle on UBS, voluntarily approaching federal prosecutors with lots of details on how the bank diverted money. Birkenfeld wasn't given immunity for his story, however, and so he was charged and pleaded guilty last year to conspiring to defraud the U.S. government.

Now, in jail for several more years, Birkenfeld is trying to get several billion dollars in reward money for his whistle-blowing, The New York Times reports.

And experts tell the Times that he's got a pretty good case.

He gave prosecutors good information, which ultimately led to UBS admitting to criminal wrongdoing and agreeing to pay a $780 million fine.

Could the IRS have ferreted out the case without him? Hard to tell. It definitely would have been much harder.

So now this guy's in jail -- as he should be, since he did break the law. But when he gets out, should he have billions waiting for him?

The IRS is offering whistle-blowers a reward of 15% to 30% of the taxes, fines and other money it collects in cases of tax dodging. But it won't give the money to anyone who was "planning" or "initiating" the fraud, the Times reports.

Birkenfeld wouldn't get any percentage of money recovered from his own clients. Instead, he wants a chunk of the accounts that he described to the IRS and the Justice Department.

The IRS is a little squeamish about this, saying that Birkenfeld didn't give any actual names or account numbers. Instead, he provided information about the behind-the-scenes workings at the bank.