In his essay in The New York Review of Books, Manhattan federal judge Jed Rakoff explains why it's problematic that 97% of federal criminal defendants agree to plead guilty if their cases aren't dismissed.

With so many people pleading guilty, some innocent defendants invariably sign onto plea bargains just to avoid the prospect of lengthy prison sentences. These are often poor defendants who aren't optimistic about winning at trial and face intense pressure from prosecutors to enter a plea.

Despite this problem, judges very rarely reject plea bargains. That's because "they don't really have any familiarity with the underlying facts," Rakoff told me over the phone recently. Even a "conscientious judge" wouldn't have enough information to drill both sides about the plea agreement, he said.

Here's what happens when defendants plead guilty, according to Rakoff: the accused reads a statement with the "bare bones of what he has decided to admit to," while prosecutor reads a statement indicating what they're prepared to prove. The judge will advise the defendant of the rights he's giving up — such as the right to a trial.

"All of this has been worked out beforehand so that it all goes very smoothly ... yet it tells the judge nothing but the very basic facts," Rakoff said. "...The whole thing takes about 20 minutes."