have taken the 5th, but Marshall mentions "investigators" not the Grand Jury. That may be a distinction without a difference since the next step is just to subpoena the witness to appear before the Grand Jury. However, it might be relevant because federal Grand Juries do not ordinarily subpoena the targets of their investigations.
Libby and Hannah have been identified as possible targets of this Grand Jury, but Marshall does not indicate whether those two are the ones invoking the 5th. If White House staff other than Libby and Hannah are invoking the fifth it may indicate a larger criminal conspiracy than some have thought.
I have always thought that the White House Iraq Group ("WHIG") run by Andy Card was involved in the Plame leak since the WHIG was involved from the beginning on choosing what lies to tell (including the yellowcake lies), who would tell them, and at what place and time. The WHIG also was responsible for planning how the lies about Iraq and the invasion would benefit Bush and the republican party politically. Libby was a member of the WHIG as were Rove, Hughes, Hadley, Maitlin and several others.
In an interview with the New York Times published Sept. 6, Card did not mention the WHIG but hinted at its mission. "From a marketing point of view, you don't introduce new products in August," he said.
The group met weekly in the Situation Room. Among the regular participants were Karl Rove, the president's senior political adviser; communications strategists Karen Hughes, Mary Matalin and James R. Wilkinson; legislative liaison Nicholas E. Calio; and policy advisers led by Rice and her deputy, Stephen J. Hadley, along with I. Lewis Libby, Cheney's chief of staff.
The first days of September would bring some of the most important decisions of the prewar period: what to demand of the United Nations in the president's Sept. 12 address to the General Assembly, when to take the issue to Congress, and how to frame the conflict with Iraq in the midterm election campaign that began in earnest after Labor Day.
A "strategic communications" task force under the WHIG began to plan speeches and white papers. There were many themes in the coming weeks, but Iraq's nuclear menace was among the most prominent.
http://www.washingtonpost.com/ac2/wp-dyn?pagename=article&node=&contentId=A39500-2003Aug9An alternative explanation for some White House staff invoking the 5th is that it is just a result of overly cautious lawyering.