Would You Believe This Witness?

HE REALLY WAS A COLONEL IN THE Egyptian army. Cairo records confirm it. But everything else about Emad Salem is disputed or highly mysterious.

He says he was a member of assassinated President Anwar Sadat's bodyguard. But the commander of the guard does not remember him.

While serving as an aide to Sheik Omar Abdel Rahman, Salem insisted to American reporters that Islam is a religion of mercy. Then he showed them photographs of people with cigarette burns and other marks of torture. Some journalists got the idea he was boasting of his own handiwork.

FBI agents were in touch with him as early as 1991. But they did not know if they could trust him: some feared he was an Egyptian intelligence agent pursuing an agenda that was not Washington's. They recruited him as a full- time informer only after the Feb. 26 bombing of the World Trade Center, when they desperately needed someone inside an Islamic radical group. Then he annoyed them by tape recording conversations with his FBI contacts as well as with alleged terrorists. One federal agent calls Salem "a pain in the ass."

A worshipper at Abu-Bakr Mosque in Brooklyn, New York, where Salem showed up a few years ago, says most of the members did not trust him. Though he tried to seem devout, the source claimed that Salem could not pray or recite the Koran properly. But members of Sheik Abdel Rahman's alleged terrorist conspiracy seem to have had no doubts. A grand jury indictment last week tells of a number of meetings at which alleged conspirators voiced fear that there might be an informer among them, then pointed a finger at one of their ringleaders. Salem was present at all sessions; once he was even asked by Abdel Rahman to investigate the charges.

Salem is now in the federal witness-protection program and unavailable to clear up these mysteries. Which raises the biggest question of all: What will a trial jury make of his crucial testimony?