More than a year before the Sept. 11 terrorist attacks, FBI agents were aware that a Middle Eastern student at a U.S. college was making anti-American statements and had contacts with militant groups overseas.
Just hours after the twin towers fell, the FBI placed the student under around-the-clock surveillance.
The decision required as many as eight agents per shift to monitor the man's travels, from apartment to college, mosque to supermarket. Another half-dozen agents listened in on his calls. Other agents filed wiretap reports or handled aerial surveillance. Two supervisory agents oversaw the case.
In all, almost 40 agents were needed to tail one target. "If this had been Manhattan or another city with a subway, we may have needed even more people," said an agent who took part in the surveillance. "I mean, if someone's on foot in New York, how you gonna follow them in a car?"
After several months, with resources stretched hopelessly thin, the FBI agents shifted gears. They ended the surveillance and worked with the Immigration and Naturalization Service to simply deport the student on minor immigration violations.
"I think he was ready to leave the area ... so we wanted to make sure we did something," the agent said. Besides, he said, "the cost was enormous."
Since last September's attacks, federal authorities have wrestled with a stark dilemma: Should they watch, or simply deport, scores of illegal immigrants who may have crossed paths with terrorists?
"For the FBI, at this moment in time, there are no good options in a lot of these cases," said Sacramento Supervisory FBI Agent Frank Scafidi. "A lot of times it comes down to dollars and cents.... We just can't afford [surveillance] for as many people as we suspect might have bad intentions."
Added one federal prosecutor: "The prevailing sentiment is, 'Just get them the hell out' " if they have visa or other immigration violations.
But if anyone deported on such charges turns out to be a terrorist -- or an accomplice -- they may come back to haunt the U.S. by assuming new identities and reentering the country.
"Then, you are in some ways in a much worse position," said the prosecutor, "because now you don't know where they are."
Since last September, the INS has deported almost 500 people as a direct result of the Justice Department investigation into terrorism. Hundreds more have been forced to leave as a result of stepped-up enforcement of immigration laws. It is likely that many people caught in the dragnet do not support terrorism, but the government is taking few chances.
Nasir Al Mubarak, for example, had lived illegally in the U.S. for a decade without incident. The Pakistani-born pilot faced deportation for overstaying his student visa but was free on bail pending an appeal on grounds that his marriage made him eligible for permanent residency.
That all changed on Sept. 11.
Right after the attacks on New York and Washington, FBI agents questioned the 35-year-old Sacramento-area resident about his association with terrorist Abdul Hakim Murad. In 1995, Murad, a Pakistani, was convicted of conspiring to blow up 12 U.S. airliners over the Pacific Ocean.
In 1991, Mubarak acknowledged, he and Murad came to the U.S. to attend flight schools, and lived together before Murad left the country. Mubarak said he had long since lost track of Murad, but after Sept. 11, federal authorities did not believe him and pressed for his deportation. Ultimately, Mubarak agreed to leave and returned in August to Pakistan, a country where he had last lived as a toddler.
Mubarak's friends and family have insisted his case is a classic example of guilt by association. But FBI officials claimed the truth is far more complicated.
"Look, I went a number of years in grade school with a guy who became part of the Manson clan. Does that make me a felon? No," Scafidi said. "But this guy [Mubarak] was encircled earlier in his life with a real-life, fire-breathing, ill-meaning terrorist."
Agent Michael Mason, who heads the FBI's Sacramento Office, said "there were sufficient connections that necessitated his removal to another country."
Truth be told, Mason noted, were Mubarak not a foreign national, U.S. authorities may not have been able to take any action against him, regardless of their suspicions.
"If he were a U.S. citizen, he might be walking around the [Sacramento] area today," Mason said. "But ... inasmuch as his residency in this country was an issue, that just became another arrow in my quiver to neutralize the threat."
The decision whether to seek deportation is rarely an easy one for federal authorities.
"That," said one FBI counterterrorism specialist, "is a question we debate every day."
One Justice Department official, also speaking on condition of anonymity, said federal authorities since last September have often detained acquaintances of terrorists if, for no other reason, than to buy time for their investigations.