Judy Miller just finished testifying before Patrick Fitzgerald's grand jury and walked, beaming, into the plaza in front of Washington's federal courthouse. If she was expecting some kind of hero's welcome from colleagues gathered there, she must have been disappointed. Although Miller took only a few questions from reporters, her exchange with them was tense. It ended rather abruptly when Times publisher Arthur Sulzberger, Jr., cut off the questions by saying,"OK, I think we're done here, folks."

Miller was asked to confirm that Scooter Libby was the source she'd been protecting. She declined to answer. Didn't Libby's lawyer tell Miller's lawyer a year ago that he was releasing her from her pledge of confidentiality? Miller said to ask her lawyer. Why was her testimony important? Miller said to ask Fitzgerald. Couldn't Miller have testified long ago? Miller said no, insisting that she didn't get a waiver she considered sufficiently personal and voluntary until this month.

If anything substantive came out of Miller's brief appearance before the press, it was this: She emphasized, at least twice, that there had been not one but two prerequisites to her testifying before the grand jury. First, Miller said, she needed a personal and voluntary waiver from the source she was protecting -- a source the New York Times and the Washington Post have both identified as Libby, Dick Cheney's chief of staff. Second, Miller said, she needed an assurance from Fitzgerald that her testimony to the grand jury would be limited to her conversations with Libby -- which is to say that it would not require her to give up the identity of any other sources she might be protecting.

Miller said Fitzgerald's agreement to limit her testimony was "very important to me," and that she would have stayed in jail "even longer" if she hadn't gotten both her source's waiver and Fitzgerald's agreement not ask about other sources. "I could not have testified without both of them," she said.

So one question has been answered today: Libby, it seems clear, was the source Miller was protecting. But who is the source she's protecting now? Add that to the list of questions that journalists -- among them, Miller's editors -- might want to start asking now.