A federal judge threw out a perjury indictment Tuesday against a Jordanian college student who knew two alleged Sept. 11 hijackers, citing errors made when investigators applied for an arrest warrant.

U.S. District Judge Shira Scheindlin dismissed the indictment after concluding that Osama Awadallah, 21, was unlawfully arrested after he was taken from his San Diego home several days after the Sept. 11 terrorist attacks.

"Awadallah was effectively seized," she wrote.

Scheindlin said that federal statute does not authorize the detention of material witnesses for a grand jury investigation. It was not immediately clear what effect such a ruling could have on dozens of material witnesses held since the terrorist attacks on the World Trade Center and the Pentagon.

"We believe the court's opinions are wrong on the fact and the law and we are reviewing our appellate options," U.S. Attorney James B. Comey said in a statement.

A message left with a lawyer for Awadallah was not immediately returned.

The judge also threw out evidence seized after Awadallah, a student at Grossmont College in El Cajon, Calif., was taken into custody on Sept. 21. The evidence included videotapes and a picture of Usama bin Laden.

The judge cited several factors showing that Awadallah's consent to go with FBI agents to their office and later submit to a lie detector test was the "product of duress or coercion."

She said the agents repeatedly made a show of force by telling him he could not drive his own car, frisking him, refusing to let him inside his apartment and ordering him to keep a door open as he urinated. Moreover, she said, one agent threatened to "tear up" the apartment if he did get a warrant.

Agents also failed to tell Awadallah he had a constitutional right to refuse any searches when they asked him to sign a form consenting to a search, the judge said.

Awadallah was charged with perjury for allegedly lying about his knowledge of one of the men blamed for the suicide attack on the Pentagon.

In grand jury appearances, Awadallah admitted meeting alleged hijacker Nawaf al-Hazmi 30 to 40 times but denied knowing associate Khalid al-Mihdhar. Confronted with an exam booklet in which he had written the name Khalid, he later admitted he knew both of them.

If convicted, Awadallah could have faced up to 10 years in prison.