WASHINGTON - The Federal Bureau of Investigation has improperly kept nearly 24,000 people on a terrorist watch list based on outdated or sometimes irrelevant information, while it missed others with legitimate terror ties who should have been on the list, according to a Justice Department report released Wednesday.
The report said the mistakes posed a risk to national security, because of the failure to flag actual suspected terrorists, as well as an unnecessary nuisance for non-suspects who may be questioned at a traffic stops or stopped from boarding an airplane.
By the beginning of 2009, the report said, the government's terrorist watch lists included about 400,000 people, listed as 1.1 million names and aliases, an exponential growth from the days before the attacks of Sept. 11, 2001, when it included fewer than two dozen people.
Intelligence officials say the watch lists have allowed different agencies to work together in an effort to prevent the type of breakdown that allowed two of the Sept. 11 hijackers to enter the United States even though they were known to the Central Intelligence Agencies for their terrorist ties.
The new Justice Department report provided the most authoritative statistical account to date of the problems connected with the watch lists and confirmed some assertions made by critics of the process. An earlier report by the inspector general, released in March 2008, looked mainly at flaws in the system.
The list has long been a target of public criticism, particularly after well-publicized incidents in which politicians including Senator Edward M. Kennedy of Massachusetts and Representative John Lewis of Georgia accidentally showed up on the lists. People with names similar to actual terrorists have complained that it can take months to remove their names from the list, and civil rights advocates charge that anti-war protesters, Muslim activists and others have been put on the lists and stopped at airports for political reasons.
The report, by the Justice Department inspector general's office, looked mainly at the F.B.I., which took the lead in 2004 for maintaining a consolidated terrorist watch list for all agencies throughout the federal government.
One of the biggest problems identified in the report was the use of outdated information, or material unconnected to terrorism, to keep people on the F.B.I.'s own terror watch list. The report examined nearly 69,000 watch lists referrals brought or processed by the F.B.I. and found that 35 percent of the people, both Americans and foreigners, remained on the list despite inadequate justification.
"Many of these watch-listed records were associated with outdated terrorism case classifications or case classifications unrelated to terrorism," the report said. In some cases, the people on the watch lists were the subjects of F.B.I. investigations that had been closed years earlier without action, yet their names had either never been removed, or not in a timely fashion.
Potentially even more problematic were the cases of people who were not on the watch lists despite evidence of terrorist ties.
The inspector general looked at a sampling of 216 F.B.I. terrorism investigations, and found that in 15 percent of those cases, a total of 35 subjects were not referred to the terror watch list even though they should have been.
In one case, for instance, a United States Army Special Forces soldier was investigated and ultimately convicted for stealing some 16,500 round of ammunition, C-4 explosives and other material from Afghanistan and shipping them to the United States in what investigators suspected might be the makings of a domestic terror plot. Yet the suspect was not placed on the watch list for nearly five months after the investigation was opened against him.
"We believe that the FBI's failure to consistently nominate subjects of international and domestic terrorism investigations to the terrorist watch list could pose a risk to national security," the inspector general said. The director of the Washington office of the American Civil Liberties Union, Caroline Fredrickson, said her group's monitoring of the watch lists indicates that the problems identified at the F.B.I. are endemic to entire system.
"What this report really shows is that on both ends, the lists are really over-inclusive and under-inclusive," she said in an interview. "With 1.1 million names, there's all sorts of problems that have larded it up, and the whole thing just really needs to be torn down and start a new system."
The F.B.I. adopted all 16 of the inspector general's recommendations for improving watch list operations, including better training and faster processing of referrals. The agency said in a statement that "we remain committed to improving our watch list policy and practices to ensure the proper balance between national security protection and the need for accurate, efficient and streamlined watch-listing processes."