The prosecutor's brief: what does Patrick Fitzgerald know? When did he learn it? And other questions.(THE CAPITAL)

AT various times during the last two years, official Washington has been obsessed with the CIA leak investigation--while at the same time knowing almost nothing about it. Who leaked CIA employee Valerie Wilson's name to columnist Robert Novak? Was special prosecutor Patrick Fitzgerald going in this direction--or that direction? What about Karl Rove? Nobody really knew the answers, at least nobody outside Fitzgerald's office.

But that changed in late January, when the court handling the case released a number of motions and letters between Fitzgerald and the legal team representing I. Lewis Libby, the former vice-presidential chief of staff who is charged with perjury, obstruction of justice, and making false statements. The documents that have been made public--and there will be more in the days to come--give us a glimpse inside the case that we've been hearing so much uninformed speculation about for so long. And they reveal a lot about not only the investigation, but the investigator too.

The documents outline an ongoing fight between Fitzgerald and the Libby defense over how much information Fitzgerald should be forced to give Libby before trial (now scheduled for early next year). That's not surprising. Libby's lawyers are using the time-honored defense tactic of asking for the kitchen sink; they appear to want virtually everything Fitzgerald has uncovered in the course of his investigation. For example, they have asked for copies of the highly classified Presidential Daily Brief for nearly a year spanning 2003 and 2004--material that Fitzgerald has said he doesn't even have. On an issue like that, a judge is unlikely to rule in Libby's favor.

But Libby has made two relatively simple requests that seem to go to the heart of the case--and Fitzgerald is ...