If you wanted a textbook example of what is wrong about appointing a special prosecutor, the prosecution of White House aide Lewis "Scooter" Libby is a classic. Let's go back to square one to see how this sorry chapter in criminal law unfolded.
The charge that was trumpeted through the media was that the Bush administration had leaked the fact that Joe Wilson's wife worked for the C.I.A. in retaliation against him for saying that Saddam Hussein was not seeking uranium in Niger, contrary to intelligence reports cited as one of the reasons for invading Iraq.
Since there is a law against revealing the identity of a C.I.A. agent, a great hue and cry went up for a special prosecutor to find and prosecute whoever leaked that information.
Some in the media gleefully anticipated seeing White House adviser Karl Rove, or perhaps even Vice President Dick Cheney, being frog-marched out of the White House in handcuffs.
Attorney General John Ashcroft appointed a special prosecutor, Patrick Fitzgerald, to investigate these charges.
Here is where the story takes a strange and disturbing twist. Today we know what we did not know when it happened -- namely, that Fitzgerald discovered early on that the leaker was not any of the White House officials on whom suspicion was focussed.
It was Richard Armitage in the State Department. Moreover, Joe Wilson's wife had a desk job at the C.I.A. and revealing that fact was not a violation of the criminal law.
In other words, there was no crime to prosecute and there was no mystery to solve as to who had leaked Wilson's wife's name to columnist Robert Novak.
At this point, a regular prosecutor would have decided that he had other things to do than to pursue an investigation of a non-mystery about a non-crime. But special prosecutors are different.
Patrick Fitzgerald insisted on keeping the investigation going for three years -- and keeping secret the fact that there was no crime involved and no mystery about who leaked.
In the course of this pointless investigation, it turned out that some of Scooter Libby's statements conflicted with the statements of some reporters. So Libby was prosecuted for perjury and obstruction of justice -- and a Washington jury convicted him.
Not only did Libby's recollections differ from that of some reporters, some of those reporters differed among themselves as to what had been said and some differed in their later testimony from what they had said in their earlier testimony.
The information about Joe Wilson's wife was so incidental and trivial at the time that it is hardly surprising that it was not fixed in people's minds as something memorable. Only later hype in the media made it look big.