A federal jury acquitted former Florida professor Sami al-Arian yesterday of conspiring to aid a Palestinian group in killing Israelis through suicide bombings, dealing the U.S. government a setback in its efforts to use secretly gathered intelligence in criminal cases against terrorism suspects.

The trial was a crucial test of government power under the USA Patriot Act, which lowered barriers that had prevented intelligence agencies from sharing secretly monitored communications with prosecutors. The case was the first criminal terrorism prosecution to rely mainly on vast amounts of materials gathered under the Foreign Intelligence Surveillance Act (FISA), whose standards for searches and surveillance are less restrictive than those set by criminal courts.

The Tampa jury deliberated 13 days before rejecting arguments laid out over five months by prosecutors that the former University of South Florida computer engineer and three co-defendants conspired with leaders of Palestinian Islamic Jihad -- which the United States has designated a terrorist group -- providing it money, strategy and advice. The accusations were based on 20,000 hours of phone conversations and hundreds of faxes secretly monitored beginning in 1993.

Al-Arian, 47, was found not guilty on eight of 17 counts, including conspiracy to maim or murder. Jurors deadlocked on the rest of the charges, including ones that he aided terrorists.

Al-Arian wept and was hugged by attorney Linda Moreno after the verdict, according to news accounts, before returning to jail, where he will wait as prosecutors decide whether to retry him on the counts that resulted in deadlock.

Two co-defendants, former Florida graduate student Sameeh Taha Hammoudeh and Chicago dry cleaner Ghassan Zayed Ballut, were acquitted of all charges. The jury acquitted a third man, Hatim Naji Fariz, manager of an Illinois-based Muslim charity, of 25 counts, and failed to reach a verdict on eight others.

Juliette Kayyem, a terrorism legal analyst at Harvard University's Kennedy School of Government, said the outcome shows that U.S. juries can seriously consider both government accusations of terrorism and any evidence.

"This case has been sort of a tortured case for the United States," said Kayyem, a Justice Department official from 1995 to 1999. "But the truth is that it never seemed that the evidence was that strong -- at least that the public evidence was that strong against him."

But David N. Kelley, who oversaw numerous terrorism cases before leaving the U.S. attorney's office in New York this year, cautioned against reading too much into the results.

"Conspiracy cases are always difficult, because you often don't have that smoking gun or other tangible thing to point to," Kelley said. "And once you get in front of a jury, that slam-dunk case suddenly plunges to 50-50, and that dog case suddenly improves to 50-50. You just don't know what's going to happen."

Outside the courtroom, Ahmed Bedier, regional director of the Council on American-Islamic Relations (CAIR), a Muslim civil rights group, praised the al-Arian verdict. Al-Arian, a Kuwaiti-born Palestinian, had become a controversial symbol for advocates of academic and speech freedom and for American Muslims who support the Palestinian cause.

"It will not only restore faith in the justice system by American Muslims but also by Muslims all over the world who doubted justice in America," Bedier said. "This sends a very positive message that Muslims can receive a fair trial in America."

Al-Arian attorney William Moffitt rested his defense without presenting evidence. In court, he argued that the government sought to muzzle his client's avowed antipathy to Israel.

"The government itself has said you are free to praise groups that engage in terrorism as a means of achieving their ends," Moffitt said during the case. "This case concerns Dr. al-Arian's right to speak, our right to hear what he has to say and the attempt of the powerful to silence him."

Tasia Scolinos, a spokeswoman for the Justice Department, said it stands by the charges and may retry al-Arian and Fariz. Noting recent convictions of two terrorism suspects in Northern Virginia and New York, Scolinos said: "The Justice Department has a strong track record of success in prosecuting terrorists and those who support terrorist activities."

A male juror told the Associated Press he perceived al-Arian's acquittal not as a First Amendment issue but as a failure of the government to prove its case.

"I didn't see the evidence," said the man, who declined to give his name. The court kept jurors' identities secret.

Then-U.S. Attorney General John D. Ashcroft hailed al-Arian's 2003 indictment as an early victory for the Patriot Act. Prosecutors alleged that al-Arian was a de facto U.S.-based leader of Palestinian Islamic Jihad, coordinating attacks, providing advice and moving money for the group, which has killed hundreds of civilians in suicide attacks. The United States declared it a terrorist organization in 1995.

Prosecutors said al-Arian, who has lived in the United States since 1975, used the university and his academic standing as cover. The university fired him after he was indicted.

Likening the case to a classic Mafia trial, prosecutors brought charges of racketeering, money laundering and extortion -- because the jihad groups threaten to kill Israelis who do not leave the country -- against defendants whom they said were part of a broader criminal enterprise.

Al-Arian led two Muslim institutes affiliated with the university that the government contended were fronts for Palestinian Islamic Jihad. Defendants allegedly disseminated news of the group's attacks and other propaganda, raised money for the organization, and helped its leaders communicate by telephone and fax.

The case became pivotal in last year's Florida Senate race. Former housing secretary Mel Martinez (R) defeated former university president Betty Castor (D) after charging that she did not do enough to sever al-Arian's ties to the school. Castor noted that al-Arian campaigned for President Bush in 2000 and met with White House adviser Karl Rove in 2001 on religion-based initiatives.

Five other defendants were indicted, including al-Arian's brother-in-law, but they are overseas and are not in custody. The brother-in-law, Mazen Al-Najjar, was held on secret evidence for three years before being deported in 2002.

David D. Cole, a Georgetown University law expert who represented al-Najjar in the deportation case, said that yesterday's verdict was a sharp blow to the government.

"They have long proclaimed this as Exhibit A in the successful use of the Patriot Act and as one of their most important prosecutions in the war on terror," Cole said. Prosecutors proceeded "on a kind of extremely sweeping guilt-by-association theory . . . without any showing that he specifically furthered or sought to further any violent act of any kind."

Staff writer Caryle Murphy and researcher Julie Tate contributed to this report.

Nahla al-Arian, wife of Sami al-Arian, hugs supporters outside the courthouse in Tampa after his acquittal.Because the jury deadlocked on nine charges, former professor Sami al-Arian will remain in jail.