NEW YORK- Slumping in his prison clothes and pallid from a year behind bars, Shahawar Matin Siraj didn't look like much of a threat as he silently endured a routine hearing in federal court this month.
But the 23-year-old Pakistani immigrant stands accused of a scheme to attack a busy New York subway station with bombs hidden in backpacks.
As police seek to secure the nation's largest transit system in the wake of the London Underground bombings, they say they are concerned about angry, isolated men like Siraj as much as organized terror networks like al-Qaida.
"One of the department's ongoing concerns is the emergence of 'lone wolves,'" said Paul Browne, the New York Police Department's chief spokesman.
The first known plot against New York's subways was averted in 1997, police said, when officers acting on a tip burst into Palestinian-born Gazi Ibrahim Abu Mezer's Brooklyn apartment and shot him in the leg as he reached for a toggle switch on a pipe bomb. He was sentenced to life in prison after testifying he wanted to kill Jews riding the subway in Brooklyn.
Despite initial reports of Hamas ties, Mezer was acting with a single alleged accomplice, who was convicted of an immigration violation and deported after three years in prison.
Siraj was working at an Islamic bookstore in Brooklyn when he was approached in 2003 by an Egyptian-born police informant. The informant spent months secretly monitoring Siraj and his co-defendant James Elshafay.
As a result, police say they have recordings of the two men and the informant discussing how attacks on the Herald Square station - the Manhattan subway stop next to Bloomingdale's - and the Verrazano Narrows Bridge could damage the economy as part of a holy war against the United States.
Siraj and Elshafay were arrested last August and charged with conspiring to damage the Herald Square station, a charge with a maximum 20-year sentence.
Defense attorney Khurrum Wahid described Siraj as a hardworking immigrant entrapped by an informant who whipped his client into a rage over abuses against Muslims like the scandal at Abu Ghraib prison in Iraq, Wahid said.
"He manages to convince them that they need to do something," Wahid said. "He puts the idea of attacking the United States into their head."
Elshafay has stopped appearing at court hearings, and Wahid said he believes the 20-year-old man is cooperating with authorities.
Besides the 1993 World Trade Center bombing and the attack of Sept. 11, 2001, the nation's most significant terrorist plots and attacks were by men acting alone or in pairs without ties to known radical networks, said Bruce Hoffman, a terrorism expert at the Rand Corporation.
Their ranks include Theodore Kacyznski, Timothy McVeigh and Eric Rudolph, as well as Palestinian-born Ali Abu Kamal, who shot a group of tourists at the Empire State Building in 1997, killing one. Others include Egyptian immigrant Hesham Mohamed Hadayet, who opened fire at an El Al ticket counter in Los Angeles in 2002, killing two.
"I think this is one of the major challenges that we face in the U.S.," Hoffman said. "The major incidents in the U.S. have not conformed to our stereotype of an established terror organization attacking a major iconic landmark."
The FBI worries most about a catastrophic attack by seasoned al-Qaida agents armed with a biological, chemical, nuclear or radiological bomb, said Tim Herlocker, special agent-in-charge of intelligence for the counterterrorism division of the FBI's New York office.
But second on the bureau's list of concerns are newer al-Qaida affiliates, he said, followed by lone wolf attackers.
The latter, Herlocker said, "probably do the least damage."
Nonetheless, he said, "The lone wolf, when influenced by day-to-day events, is harder to stop, harder to know about, much more difficult to defend against."
Associated Press Writer Tom Hays contributed to this report.