The former professor, Sami Al-Arian, a fiery advocate for Palestinian causes who became a lightning rod for criticism nationwide over his vocal anti-Israeli stances, was found not guilty on eight criminal counts related to terrorist support, perjury and immigration violations. The jury deadlocked on the remaining nine counts against him after deliberating for 13 days, and it did not return any guilty verdicts against the three other defendants in the case.

“This was a political prosecution from the start, and I think the jury realized that,” Linda Moreno, one of Al-Arian’s defense lawyers, said in a telephone interview. “They looked over at Sami Arian, they saw a man who had taken unpopular positions on issues thousands of miles away, but they realized he wasn’t a terrorist. The truth is a powerful thing.”

The trial, lasting more than five months, hinged on the question of whether Al-Arian’s years of work in the Tampa area in support of Palestinian independence crossed the threshold from protected free speech and political advocacy to illegal support for terrorists.

Prosecutors, who had been building a case against Al-Arian for 10 years, relied on 20,000 hours of taped conversations culled from wiretaps on Al-Arian and his associates. Officials charged that he had helped finance and direct terrorist attacks in Israel, the Gaza Strip and the West Bank, while using his faculty position teaching computer engineering at the University of South Florida as a cover for his terrorist activities.

But ultimately, the jury in Tampa that heard the case found him not guilty of the charge of conspiring to kill people overseas, and it deadlocked on three of the other most serious terrorism charges against him.

“People here are pretty stunned and amazed by the verdicts,” said a federal law enforcement official in Washington who has monitored the case closely, speaking on condition of anonymity. “We thought we had him dead to rights.”

In bringing the case against Al-Arian in 2003, the Justice Department relied on the easing of legal restrictions under the antiterrorism law known as the USA Patriot Act to present years’ of wiretaps on the defendants in a criminal context. In the conversations cited by prosecutors, Al-Arian was heard raising money for Palestinian causes, hailing recently completed attacks against Israel with associates overseas, calling suicide bombers “martyrs,” and referring to Jews as “monkeys and swine” who would be “damned” by Allah.

But much of the conversation and activity used by prosecutors predated the 1995 designation by the United States of Palestinian Islamic Jihad as a terrorist group, a designation that prohibited Americans from supporting it. Several legal analysts and law professors said Tuesday that the government appeared to have overreached in its case.

“I think the government’s case was somewhat stale because a lot of these events dated back 10 years, and the case was so complex that it was all over the board,” said Peter Margulies, a law professor at Roger Williams University in Rhode Island who has studied terrorism prosecutions.

In the mid-1990s, news coverage about Al-Arian drew attention to his fiery opposition to the Israeli occupation and led some critics to label the University of South Florida as “Jihad U.”

But many Muslims in Florida continued to support him, and as an influential Muslim activist, he continued to have access to senior Democratic and Republican officials. However, criticism accelerated after the Sept. 11 attacks, particularly in light of his appearance on Fox News just weeks after the 2001 attacks, in which the show’s host, Bill O’Reilly, confronted him with his past statements concerning “Death to Israel.”

His indictment in 2003 led the university to fire him, a move that had been debated for years, and disclosure of his close dealings with Palestinian militants as cited in the indictment prompted even some university backers to rethink their support for him.

Family members of Al-Arian and the other three defendants — Sameeh Hammoudeh, Ghassan Ballut and Hatim Fariz — wept in court as the not-guilty verdicts were read, and Muslims in the Tampa area planned a prayer service and celebration Tuesday night at the local mosque Al-Arian helped found.

Al-Arian is to remain in jail on an immigration hold, but Moreno said the defense would probably file a motion next week seeking to have him released on bond.