After nine years in hiding, witness 684 is set for key Lockerbie role

When Abdul Majid Razkaz Salam Giaka enters the courtroom at Camp Zeist in the Netherlands this week, a lot will be riding on his words. Mr Giaka's testimony is key to the prosecution case against the two Libyans accused of blowing up PanAm flight 103 over Lockerbie in December 1988, killing 270 people.

When Abdul Majid Razkaz Salam Giaka enters the courtroom at Camp Zeist in the Netherlands this week, a lot will be riding on his words. Mr Giaka's testimony is key to the prosecution case against the two Libyans accused of blowing up PanAm flight 103 over Lockerbie in December 1988, killing 270 people.

But for his American handlers, there is yet more at stake. Mr Giaka's performance will also serve as a judgement on intelligence operations going back well before Lockerbie, and as a sign of how future operations against terrorism will be handled.

Abdelbasset Ali Mohmed Al Megrahi and Al Amin Khalifa Fhimah, the two Libyans on trial at Camp Zeist, are charged with murder, conspiracy to murder and breaches of the Aviation Security Act. The prosecution alleges that they carried out the bombing from Malta. They say they are innocent, and that others were responsible for the operation.

Crown witness 684 is perhaps the most mysterious figure in a case with more than its fair share of unexplained and shady aspects. He is expected to land at a Dutch military airport and from there be transferred by helicopter to Camp Zeist. He will probably testify in a hairpiece, dubbed a "Shirley Bassey wig" by one of the judges, and heavy make-up; the security around him will be as tight as the US can manage.

Mr Giaka was, like Mr Megrahi and Mr Fhimah, an employee of Libyan Arab Airways in Malta. He was also an employee of the Libyan intelligence services, as were the two accused, according to the prosecution. And he alleges direct knowledge of the plot to blow up the airliner. "He is the boy," according to one source familiar with the case.

Months before the bombing, Mr Giaka is said to have gone to the American embassy in Malta and offered himself as an agent. He received cash payments of around $20,000 a year, reportedly from the US, but for at least two years after the bombing Mr Giaka is said to have told the US nothing of his knowledge of the operation.

In July 1991, according to the Maltese media, Mr Giaka and his Maltese wife, Cynthia, flew from Tunisia to Malta. They were met by US officials and taken to the USNS Butte, a navy ammunition ship stationed off the coast.

Mr Giaka was questioned by FBI agents Phillip Reid and Harold Hendershot, and began to tell of a plot to blow up an airliner. Mr Fhimah had showed him a box which contained "enough explosive to explode all of Malta," he said. By the autumn of that year, the US and Britain had issued indictments against Mr Megrahi and Mr Fhimah.

Since then, Mr Giaka has lived a life in the dark. He has been held under the FBI's witness protection programme at secret locations in the US; his very existence a matter for rumour and hearsay. But once the trial process began in earnest, Mr Giaka began to emerge from the shadows.

Last November, three lawyers from the Scottish solicitors defending the two Libyans flew from New York to Dulles airport, south of Washington. From there they were driven in a blacked-out van around side roads and country lanes for over an hour; perhaps they were still in Virginia, perhaps in Maryland, in West Virginia or in Washington itself when they arrived at the safe house where Mr Giaka had been taken for questioning.

Over two days they deposed him, in preparation for the trial. He was heavily disguised, with a wig and make-up. But they were even more surprised by what he said. According to sources with knowledge of that process, he was vague, erratic and often confused. But he had been in hiding for nearly a decade, they said, and under intense pressure.

Mr Giaka's testimony will start today or tomorrow. The two barristers defending Mr Fhimah and Mr Megrahi, Michael Keen and William Taylor, are both well-respected lawyers and will try hard to undermine his credibility. Of the two, Mr Taylor is probably the tougher. A Queens' Counsel in both England and Scotland, he is described as a "heavy criminal silk," a hard and streetwise character.

If the defence can dent Mr Giaka's credibility, it will be hard for the prosecution to prove the first and most serious of the charges against the two Libyans: murder. Mr Giaka is the closest to the alleged plot that the trial has come so far.

There are other witnesses for the second and third charges - conspiracy to murder and breaches of the Aviation Security Act. But murder will be very tough indeed. It means proving that the defendants loaded a suitcase bomb on to a plane at Luqa airport in Malta which travelled via Frankfurt and London and destroyed the plane over Lockerbie.

The defence has already tried to undermine Mr Giaka's credibility by referring to his eligibility for a reward of some $4m (£2.7m) for information leading to the conviction of those responsible. And that reward also goes to the heart of how and why the US cares so much about Mr Giaka.

It is not just that he might be able to resolve a case which aroused strong passions around the world, one of the worst attacks on American and British civilians in peace time. The witness protection programme is a crucial part of the FBI and CIA strategy against terrorism; and they are clearly hoping that, as they ramp up their efforts, it will pay further dividends.

Another series of trials further down the road could also involve secret witnesses. A number of suspects are already in custody for the bombing of the US embassies in Nairobi and Dar es-Salaam two years ago, allegedly under the inspiration of Islamist leader Osama bin Laden. To persuade people to testify against him, America must show that it can protect witnesses, reward them, and get convictions.

If Mr Giaka is as uncertain as he was in earlier depositions, the case may rapidly unwind. But then perhaps that was all a charade, like the wig and make-up; perhaps Mr Giaka will deliver the silver bullet the prosecution expects. Only when he steps into the witness box will anyone really know.