TAMPA -- Even if he is acquitted on terrorism charges, former University of South Florida Professor Sami Al-Arian could face additional years behind bars and possible deportation from the United States.

Immigration officials have the power to initiate deportation proceedings and keep him jailed as a security threat. A deportation case could be built upon the same evidence that failed to generate a conviction because the burden of proof in immigration court is "clear and convincing evidence," a step below the reasonable doubt standard in criminal court.

Officials at Immigration and Customs Enforcement, part of the Department of Homeland Security, will not comment on whether there are plans to detain Al-Arian. Jurors resume deliberations Monday in a 51-count criminal indictment that places him on the Palestinian Islamic Jihad's governing board and at the center of a North American cell for the terrorist group.

Al-Arian's affiliation with the Islamic Jihad now is acknowledged, although his attorneys minimize its scope. In addition, Al-Arian registered to vote and voted in 1994 even though he was not a citizen. State prosecutors declined to pursue charges, but these facts could be used to strip him of his permanent residency.

Al-Arian attorney William Moffitt did not respond to a request for comment.

Immigration officials have had a three-pronged deportation case against Al-Arian for nearly a decade, said William West, a retired supervisory special agent who investigated the case.Repeated recommendations to officials in Washington were turned down.

District Counsel "Dan Vera and I made pitches up the chain of command repeatedly over the years," West said. The answer "was never no," he said. "It was always 'hold off on that to pursue the larger investigation.' "

Immigration law allows the deportation of "any alien who has engaged ... in any terrorist activity." And provisions in the Patriot Act, passed after the Sept. 11attacks, allow deportations for activities that were legal at the time.

In testimony before the Senate Judiciary Committee in May, Georgetown University law Professor David Cole criticized the Patriot Act's definition of material support for terrorism that can prompt deportation. He cited the case of two Palestinian men in California facing deportation for distributing magazines tied to a terrorist faction during the 1980s.

"It is no defense to show that one's support to the group furthered only lawful, nonviolent ends, nor is it any defense to show that the group has not engaged in any terrorist activities," Cole testified. "If this law had been on the books in the 1980s, any foreign national who donated to the African National Congress for its largely lawful, nonviolent opposition to apartheid in South Africa would have been deportable."

In the Al-Arian case, immigration officials can use declassified conversations, secretly intercepted by the FBI, that reveal Al-Arian discussing Islamic Jihad business with the group's leaders. Also, bank records from 1993 show he sent four $2,000 wire transfers to families of Islamic Jihad members who attacked an Israeli military base a year earlier.

Al-Arian was born in Kuwait and grew up in Egypt. As a Palestinian, he is not a citizen of either country. There is no guarantee he could be forced out of the United States even if he is found deportable.

His brother-in-law, Mazen Al-Najjar, spent months in jail while looking for a new home after his deportation appeals were exhausted in 2001. He left for Lebanon in August 2002 but was forced to leave there a short time later. His whereabouts today are unknown.

In Cleveland, efforts to deport someone said to be a co-conspirator of Al-Arian have hit a snag. An Akron, Ohio, jury convicted Fawaz Damra of naturalization fraud last year, finding that he failed to disclose affiliations with Al-Arian's charity and the Islamic Jihad.

Damra has argued he could be tortured if forced to go to Gaza, the West Bank or Jordan.

West argues such obstacles should not be a factor.

"It's not really a question of the viability of a deportation charge; it's whether the government has the will to do it," he said.