Terror Suspect List Yields Few Arrests

Using the database, U.S. and international authorities prevented "numerous attempts" at entry into the United States by an Egyptian citizen, Omar Ahmed Ali, who went on in 2005 to commit a suicide bombing in Qatar that killed one British citizen and injured 12, Petrovich said.

Many U.S. citizens are stopped, questioned and, if no arrest warrant is pending, released. They are not told their watch-list status. To do so, the government says, could tip off suspects that they are likely to be questioned or detained.

Some travelers who are repeatedly stopped can only speculate that they are on the watch list.

Abe Dabdoub, 39, and his wife, both U.S. citizens, live in a Cleveland suburb. He said he has been detained 21 times at Michigan's border with Canada since last August. Dabdoub, who works for an electronics manufacturing company, said he has even begun to keep a spreadsheet. The first four times, he said, he was handcuffed. Once, his wife had to plead with the agents not to handcuff him in front of their 5- and 7-year-old boys, he said. The agents know him so well by now that they call him by his first name. Every time he asks them why he is being stopped, Customs officers tell him, "We can't tell you, for national security reasons," he said.

Customs officials declined to comment on his case.

Agencies nominate names to the list based on rigorous, classified criteria, Kopel said. The TSC has created a redress unit that ensures that watch-list and source information is accurate, officials said. Since 2005, the unit has resolved more than 90 percent of the several hundred complaints it has received, including by deleting names or adjusting data.

Each watch-list hit is a "positive encounter" -- what the government says is a conclusive match against the database -- by a customs officer or other official with an American or foreigner. U.S. citizens, if there is no arrest warrant, cannot be denied entry. About half of the encounters take place at land borders, airports or seaports. Other travelers are flagged at consular offices or by state and local police.

The number of hits has surged since the second half of fiscal 2004, when the database was created. That year, the FBI reported 5,396 encounters, with some people having multiple encounters. In 2005, 15,730 hits were logged. Next year, the FBI projects 22,400 hits.

FBI officials said the rising numbers result from wider information-sharing among international, federal, state and local authorities.

"A lot of times it's not to our advantage to make an arrest," FBI spokesman Paul Bresson said. "We don't want the subject to know what we know. It doesn't mean we're not paying attention. On the contrary, it shows that we're being very proactive in trying to identify threats."

But Steven Aftergood, director of the Federation of American Scientists' Project on Government Secrecy, said growing use of this database magnifies the consequences of errors that are entered into it.

"There needs to be a reliable way to correct bad information and protect the innocent," he said.