TAMPA, Fla. (AP) - The U.S. government's failure to convict a former professor accused of being a key figure in a Palestinian terrorist group suggests the Patriot Act is not the "magic bullet" some prosecutors thought it would be, an expert says.

In a stunning blow to the government, fired University of South Florida professor Sami Al-Arian was acquitted Tuesday of nearly half the charges against him, and the jury deadlocked on the rest. More than 80 witnesses testified during the five-month trial.

"I think it's a setback for the government, and I think it might illustrate that the Patriot Act might not be the magic bullet prosecutors thought it was when it was passed," said John Farmer, a former New Jersey attorney general and federal prosecutor who served on the commission that investigated the Sept. 11 terrorist attacks.

Al-Arian's indictment in 2003 was hailed by the government as a triumph of the Patriot Act, which allowed secret wiretaps and other intelligence collected over nine years to be used to charge Al-Arian and others with supporting the Palestinian Islamic Jihad. Before the law, it was more difficult for prosecutors to access information gathered by intelligence agents.

The government said the law allowed it to tear down the PIJ's North American cell and prosecute its leaders. Critics said the law allowed government agents to overstep and persecute a man who was merely a vocal activist for the Palestinian cause.

Farmer said the verdicts call into question the ability of prosecutors to use secretly gathered intelligence as evidence in a criminal case. He noted that intelligence investigations are not designed to provide proof beyond a reasonable doubt, which is the standard in a criminal court.

"I think what this really signifies is that the criminal law has significant weaknesses as a tool in fighting domestic terrorism," he said.

In this case, the intelligence was presented to jurors in the form of hundreds of transcripts of telephone calls and faxes in which Al-Arian and his co-defendants discussed the mission and future of the terrorist group, and appeared to celebrate suicide bombings that killed Israelis.

Jurors said there was plenty of evidence, but that none of it linked Al-Arian and the others directly to violent acts of the PIJ on the other side of the world.

That shouldn't impact how the Patriot Act is used in other cases, said UCLA law professor Norman Abrams, an expert in anti-terrorism law.

"I don't think the fact that (prosecutors) didn't obtain convictions should affect whatever advantages they gained from the Patriot Act," Abrams said.

"The main thing is the Patriot Act enhanced their ability to use wiretaps in criminal prosecutions. That is an advantage no matter what," he said.

Stephen King, a former federal prosecutor now in private practice, agreed that the verdicts shouldn't reflect on the Patriot Act.

"The jury simply didn't see the evidence presented at trial as sufficient. That has nothing to do with the investigative tools that were used to prepare the case and secure an indictment," King said.

The Justice Department said yesterday it hasn't decided if Al-Arian will be retried on the charges on which the jury couldn't decide, including three key conspiracy counts.

"We remain focused on the important task at hand, which is to protect our country through our ongoing vigorous prosecution of terrorism cases," the department said in a statement. "While we respect the jury's verdict, we stand by the evidence we presented in court against Sami Al-Arian and his co-defendants."