OTTAWA - An intelligence official testifying about Mohamed Harkat's alleged extremist ties told the Federal Court he did not review classified information on the case for fear of letting something slip in public.

But the veteran Canadian Security Intelligence Service agent told the court he'd prepared for his testimony by reading the non-classified summaries of the case provided to federal cabinet ministers and also two books on Islamic extremism.

Justice Simon Noel is reviewing whether the seven-year-old security certificate against the Algerian-born Harkat should be maintained or thrown out.

The seldom-used certificates allow immigration officials to deport suspected terrorists and spies who are not Canadian citizens.

Harkat's supporters maintain the security certificate process is deeply flawed because suspects are never permitted to know the full details of the allegations against them.

The latest Federal Court hearing, expected to last six weeks, is supposed to weigh all the evidence and finally determine if the former Ottawa pizza delivery man can be deported.

The first witness called by federal lawyers, a 19-year CSIS agent testifying under the pseudonym "John," quickly established that he would be unable to reveal details of the specific security concerns about Harkat.

The spy said he was never part of the CSIS investigating team looking at Harkat but had seen some classified material on Harkat a number of years ago in the course of other duties. At the prompting of federal lawyer Andre Seguin, the agent explained he hadn't reviewed the classified material before coming to court because he did not want to be "in a position to inadvertently reveal classified information during these proceedings."

The agent did note that he read two books in preparation for his testimony, "Inside Al Qaeda: Global Network of Terror" and "The One Percent Doctrine: Deep Inside America's Pursuit of Its Enemies Since 9/11."

The CSIS agent was expected to be on the stand for up to three days.

The courts have already tossed out security certificates against two men, Moroccan-born Adil Charkaoui of Montreal and Syrian Hassan Almrei, but three other such certificates -- including Harkat's -- remain outstanding.

CSIS downgraded its threat assessment of Harkat last year after initially calling him an al Qaeda sleeper agent. The spy agency subsequently said Harkat did not engage in violent acts and that prior to his seeking political asylum in Canada in 1995 his association with Islamic extremists appeared to be limited to logistical support.