Why were Karl Rove's aides called before the grand jury?

We're learning a little more -- but only a little -- this morning about why two of Karl Rove's top aides were called before Patrick Fitzgerald's grand jury last week.

According to a report in today's New York Times, Susan Ralston, who works for Rove at the White House, and Israel "Izzy" Hernandez, a former Rove aide who's now at the Commerce Department, were questioned Friday about testimony that Time's Matthew Cooper gave the grand jury earlier in July.

A source tells the Times that the aides were asked why Cooper's July 11, 2003, telephone call to Rove -- the one in which Rove apparently told Cooper that Joseph Wilson's wife worked at the CIA -- wasn't listed on the phone log for Rove's office. The source says there was no record of the call because Cooper did not call Rove's office directly but was transferred there instead by a White House operator.

If that's the most important piece of the Rove aides' testimony, it isn't exactly a bombshell -- indeed, reading deeply into the tea leaves, one could imagine that the testimony undercut a prosecution theory that the lack of a record suggested that Rove's office was trying to hide the fact that he had spoken with Cooper at all. It wouldn't be a crazy theory, exactly: As we noted a couple of weeks ago, Rove apparently forgot to mention his conversation with Cooper when he first talked with investigators about the outing of Valerie Plame.

But what may be more significant about the aides' grand jury appearances is that they happened at all. Back in April, Fitzgerald said in a court filing that, by October 2004, he had "for all practical purposes" completed his factual investigation of the Plame case but for "the testimony of [Judith] Miller and Cooper and any further investigation that might result from such testimony." Fitzgerald got Cooper's testimony last month, and it should be pretty clear to him by now that he's never going to have Miller's. By calling in the two Rove aides, Fitzgerald has made it pretty clear to anyone staking out the grand jury room that he's not done yet.