"The investigation did not always yield admissible information or testimony, or a complete picture of the activities undertaken... Some individuals invoked their Fifth Amendment right... and were not, in the Office' s judgment, appropriate candidates for grants of immunity. The Office limited its pursuit of other witnesses and information—such as information known to attorneys or individuals claiming to be members of the media—in light of internal Department of Justice policies... Some of the information obtained via court process... was presumptively covered by legal privilege and was screened from investigators by a filter (or "taint") team. Even when individuals testified or agreed to be interviewed, they sometimes provided information that was false or incomplete, leading to some of the false—statements charges described above. And the Office faced practical limits on its ability to access relevant evidence as well—numerous witnesses and subjects lived abroad, and documents were held outside the United States."