"If we were concerned with an ordinary crime committed on a Friday or Saturday night anywhere in Scotland, the relevant prosecution authorities would have marked the papers 'no prosecution'," he says.
Professor Black's comments are part of a Channel Four Dispatches programme, to be shown on Thursday, which raises serious concerns over the central planks of the prosecution case. Professor Black has been closely involved in the lengthy international negotiations to allow the two men to get a proper trial. Charges against the two Libyans, Ali Basset al-Megrahi and Al-Amin Khlaifa Fhima, were laid in November 1991 after a three-year criminal investigation by Scottish police assisted by an FBI team.
At the time of the bombing, both men were working as officials for Libyan Arab Airlines in Malta. The prosecution will claim they smuggled a bomb in an unaccompanied suitcase into Malta airport's luggage transfer system and that suitcase was transferred on to Pan Am flight 103 at Heathrow.
The central plank of the evidence against the two men hinges on a tiny fragment of electronic circuit board found in the baggage of the crash plane. At the time of the 1991 charges, the head of the FBI forensic laboratory, Tom Thurman, went on television across the world to say that the fragment was identical to timing devices sold by a Swiss elec-tronics company, Mebo, to Libya prior to the bombing.
However the new evidence challenges the claim that the fragments are identical. Edward Bollier, of Mebo, has examined the FBI photographs and says that fragment is not from the production version supplied to Libya. "I can now say for certain that they fragment does not come from one of the timers we sold to Libya." Mr Bollier says it probably comes from one of three prototype versions. Two were sold to Institute of Technical Research in East Germany. "We now know that institute was a technical workshop for the Stasi," says Bollier. The third unfinished prototype was stolen.
If Mr Bollier's close connections to the Libyans makes him an imperfect witness, his evidence is supported by an independent British forensic expert, Owen Lewis.
An FBI agent, Tom Thurman, who has now left the agency, was criticised for inadequate supervision of his staff and for altering forensic reports.
Professor Black has studied the evidence so far made public and is concerned that the indictment could fall short of the standards Scottish law demands. "I can foresee certain very difficult issues. There are certain gaping holes in the theory, the scenario upon which the Crown case against these two Libyans is based, and unless these holes can be plugged than there is not a chance of a successful prosecution."
The Channel Four programme also challenges the prosecution case that the bomb originated in Malta. Tags on the clothes within the bomb suitcase show they were of Maltese origin and sold in only one shop in Malta. The shop owner was shown a series of photographs of Arab men and is said to have picked out Mr al-Megrahi as the purchaser of the clothes. But close examination of his 19 statements to police show that the shop owner consistently said the man was much older and taller than either of the two Libyans.
The prosecution alleges that the bomb was in an unaccompanied case put on a plane in Malta and transferred onto flight 103. But the general manager of Air Malta, Wilfred Borg, says: "I'm not ruling out that mistakes can be made. But if there were any mistakes on the day we would have had a claim for a missing bag."
Again, if this is correct it would lend further credence to the alternative theory that the suitcase was put on at Frankfurt by Akmed Jabril's terror group, PLFG-CG, on behalf of the Iranians.
After the USS Vincennes shot down the Iranian Airbus in July 1988 the then Iranian Interior Minister Ali Akbar Mohtashemi repeatedly said blood would rain down in revenge.
By mid-October 1988, Mr Jabril's bomb maker, the Jordanian Marwan Khreesat, had been dispatched to Germany and had assembled five bombs, built into Toshiba radio-cassette players, designed to detonate at altitude. The German police followed Mr Khreesat. On 26 October, he and 14 other PFLP- GC suspects were arrested in an operation code- named "Autumn Leaves". One bomb was seized. At least one and possibly two more bombs were not found.
It is alleged that Mr Jabril switched the suitcase of a passenger on Pan Am 103, a Lebanese-born American, Khal-id Jafaar, who was a member a major drug producing family from Lebanon's Bekaa valley.
MAXWELL KERR opened his door in Rosebank Crescent to find the sky on fire. "There was a brilliant orange ball of fire above us. My sleeves were up and I could feel the heat on my arms. Drops were coming from the ball of fire and landing all around."
When the pictures on the living room wall started shaking and ornaments jumped aboutjust after 7pm, Mr Kerr's first thought had been of the main West Coast railway, which runs through the centre of Lockerbie. As he and neighbours rushed on to the street, they next suspected it might be one of the RAF fighters that exercised over the Borders hills. "But up the street we found containers of food. Those bread rolls were scattered around. My nephew found a passport. Then we knew it wasn't an RAF jet."
Mr Kerr found the first body on the pavement at the top of the street. "It was a girl; she had red hair and was wearing blue jeans. Then I turned her over and saw she was black."
The woman, curled in a ball and with no marks on her, was one of dozens of students from Syracuse University, New York, to perish on Pan Am Flight 103. Their party had been in the central part of the Boeing 747 - a 60- foot section of which crashed into the small housing estate of Rosebank Crescent and Park Place. Sixty-two bodies were strewn about the gardens.
Mr Kerr, a Lockerbie man all his 62 years, understood later the drops from the fireball were kerosene, spewing from a fuel-laden wing headed for Sherwood Crescent where 11 people died in their homes. "Everything was incinerated. That's what one boy saw as he was going to a friend's to get his bicycle repaired. He turned round and the whole thing exploded in front of him... his mother, father and sister... no more."
Mr Kerr became chairman of the Rosebank residents' group as the town pulled together. He was awarded a British Empire Medal, has met the Queen and Prince Charles and made friends with Americans who make regular pilgrimages to the memorials.
"We're a large family and we talked our way through it, that and the hard work."
He and his neighbours will never forget the night the sky blazed. But they believe a trial of the two Libyans, and better still a full inquiry into the bombing, would close an over-long chapter. "We thought it would all end following the first anniversary. But now I want some answers," Mr Kerr said. "There's a lot of people in Lockerbie want answers."
PAT KEEGAN had just gone upstairs to hide his mother's Christmas present "when a loud wind came and then a roar. I thought it was an RAF fighter hitting my roof. I thought I was dead." He went downstairs and found his mother had been shielded by a fridge-freezer and survived.
Pat Keegan is a Roman Catholic priest, ordained in 1970. His presbytery was in Sherwood Crescent, Lockerbie. When he looked out, he saw the rest of the houses had gone, incinerated by the 747's fuel tanks. Many of his friends and neighbours had perished.
He hurried his mother to safety and for the next 36 hours looked after his parishioners. He was there when the first of the relatives of the American victims arrived in the town.
Father Keegan was then 42. He had been an alcoholic and had received treatment before the disaster. Was he tempted to return to the bottle? "No ... But I knew deep sadness and I think that understanding enabled me to help others suffering from grief. The person who stands out to me was Alec Mackleroy, of the Dumfries and Galloway Regional Community. After the disaster we ran a community support group. When things got too tough we would have a good swear together. If things got messy he and I would go into another room and shout and bawl. That built a bond of friendship."
Several years after the disaster Father Keegan realised it had taken a toll. "I spent a good few years in the darkness ... The sheer amount of grief had made my brain shut down."
Five years after the crash he left Lockerbie. "The town had largely recovered and I felt I needed to move on. I did a year in a psychiatric hospital but then decided I wanted the variety of parish life again." He is now parish priest at St Margaret's, in Ayr.
The comfort he gave to the families of American victims has led to close ties in the United States and he is regularly asked to visit.
"Lockerbie was an enormous task to face. A task I felt inadequate for. I have learnt that God and people can help you through. The power of God certainly helped me to come through." The strength of the people of Lockerbie has had a profound effect on his life.
"I have a happy life now," he says. "I have a deep sense of gratitude that I survived. It has changed my life. Everything is much more vivid, in much sharper focus. I appreciate each individual I meet and the value of life."
The Victim's Family
"I HAD dropped my daughter at Heathrow and driven back to our home in Worcestershire," says the Rev John Mosey. "We were watching the TV news bulletin about an aircraft coming down in Scotland and it didn't connect. Then they said the flight number and my wife Lisa said. 'That was Helga's flight.' Our son Marcus, who was 15, just kept saying 'no, no, no'. My wife was saying, 'Helga, Helga, Helga'. She hated the idea that she couldn't be there when her daughter most needed her. We then stood together and prayed and asked God to help us."
The Moseys are part of a close-knit religious community, the Assemblies of God, for whom John is a minister. As soon as word got around friends flooded in to comfort them. "In the next two hours 40 people came by. In a fortnight over 600 people came to see us. We prayed. Some of the people fell apart at the seams and we had to help them," Rev Mosey recalls.
Helga Mosey was 19 when Flight 103 was blown out of the sky; she had just left school and was taking a year out before studying music at Lancaster University. She was returning to her nanny job in New Jersey.
Five days after the disaster John Mosey sat alone at his daughter's desk. "I realised that I could not scream for revenge. That would make me no better than they. I realised this was the test of our Christian faith. Evil gave us a platform."
The family started a fund for third-world causes. There is now an orphanage in the Philippines named after Helga Mosey, supported by the fund. "These children would not have lived if Helga had not died," said Rev Mosey.
The Moseys have also been central figures in the UK Families Flight 103 group, and last week went to 10 Downing Street as part of the delegation to see Tony Blair.
The Moseys were affected by their daughter's death in very different ways. "My wife's blood pressure went up and she still has to be on medication. For me it was a more emotional reaction. At first I was fine and up front, but eight years later I more or less had a breakdown.
"I am a lot better now. My wife and I had to have psychiatric reports for the damages case. It showed we both had post traumatic stress disorder. We miss our daughter terribly. We still have bad days and we call these Helga days."
They remain close to a number of Helga's schoolfriends. "I think we have had an influence on some of her friends. I think her death stopped one or two in their tracks. However, we sometimes find it very sad when they get married or have children, which Helga would now be doing had she lived."
TAM DALYELL (right) was the first MP to raise the disaster in the House of Commons. Shortly after the news broke he interrupted a debate on the Official Secrets Act to ask for a government statement. The initial statement came at 10.12pm on 21 December 1988, three hours after the explosion.
Mr Dalyell visited the site on day three: Lockerbie is 40 miles from his constituency. "I was horrified by what I saw," he says.
Mr Dalyell, Labour MP for Linlithgow, was a fully paid-up member of Parliament's awkward squad, already known for campaigning against the then Tory government on such issues as the sinking of the Argentine cruiser Belgrano during the Falklands conflict.
He says his first inkling that all was not right about the Lockerbie inquiry came a few days after the disaster. On New Year's Eve a police sergeant told him in confidence that he was not happy: Americans were poring over the wreckage in a way that "would not be acceptable" in the British investigation.
Ten years on, Mr Dalyell is sceptical about claims that the Libyans were responsible. He believes it was orchestrated by the Iranians in retaliation for the shooting down of their Airbus by the USS Vincennes.
JOURNALIST David Ben-Ari-yeah arrived in Lockerbie less than two hours after the Boeing 747 had come down on the town. The disaster was to change his life. An Edinburgh- based freelance, he worked for the initial few hours for a national tabloid handing over film to the paper's staff reporters as they arrived.
Even now, his voice is incredulous at the destruction he saw. "One can only imagine the forces that can reduce a 747 to wreckage the size of postage stamps," he said.
He attended the first press conference given by John Boyd, the Chief Constable of the Dumfries and Galloway Police, to 300 journalists. Ben Ariyeah realised this might be the biggest story he would ever cover. He remained in Lockerbie for several weeks, wedging his 6ft 6in frame into the rear of his car to sleep.
He was the first to get the story that the Pan Am jet had crashed as result of a bomb rather than the initial theory of a catastrophic decompression.
He began reporting for an American national radio station. "I found myself broadcasting over the phone up to four times an hour." Those vivid reports toAmerica would eventually win him an award.
Over the weeks that followed Ben-Ariyeah became increasingly involved with those who had been affected by the disaster and formed a lasting friendship with the families' spokesman, Jim Swire.
"When I started at Lockerbie I was egocentric, materialistic and selfish. The way that community behaved in the face of adversity has taught me a lot. I am no longer interested in possessions," he said. "I learnt that death does not discriminate. Rich and poor died at Lockerbie. Saints and sinners, too."
Ben-Ariyeah became obsessed with finding out who had planted to bomb. He was already suspicious of some of the activity he had seen immediately after the bombing. "I would sit on the wall sucking my pipe and you can learn a lot by just watching." He was told of strange American officials taking away packages and money.
He had considerable involvement in the making of Allen Frankovich's controversial and erudite film The Maltese Double Cross shown on Channel Four in 1995.
Ben-Ariyeah who now has "more than 50 candles on the cake" says that the personal consequences of the decade-long involvement in the Lockerbie case have been quite severe. His professional career as a journalist has ended for the time being. He suffers from a number of illnesses and lives on invalidity benefit in a small Edinburgh flat.