Lockerbie bomb report 'error'

Details of the reconstruction were given to the court

An air accident investigator has told the Lockerbie trial there was a significant mathematical error in the official report on the disaster.

In highly technical but potentially crucial evidence, Christopher Protheroe said he informed prosecution lawyers in a meeting on Monday that a complex formula used to calculate blast wave effects after an initial explosion had been incorrectly applied in the 1990 report.

He admitted that correct calculation of the so-called "mach stem" phenomenon would indicate that the bomb which destroyed Pan Am Flight 103 over Scotland went off closer to its fuselage skin than originally thought.

The trial

Abdelbaset Ali Mohmed Al Megrahi, 48, and Al Amin Khalifa Fhimah, 44, plead not guilty

They are charged with murdering 270 people

They face alternative charges of conspiracy to murder and a breach of the 1982 Aviation Security Act

About 1,000 witnesses are expected to give evidence

The trial could last for a year

The effect is created when a bubble of super-heated gases expands violently after explosives are detonated.

The report by the UK's Air Accident Investigation Branch (AAIB) indicated that damage discernible in debris from the forward cargo hold showed that the distance would have been about 25 inches (63 cm).

On evidence on Thursday, Mr Protheroe said the distance, if calculated correctly, would be about 12 inches (30 cm).

The prosecution alleges that Abdel Basset al-Megrahi and Al-Amin Khalifa Fahima, working as Libyan intelligence agents, planted a bomb in an unaccompanied suitcase in Malta which was eventually loaded onto the doomed aircraft in London.

Model aircraft

The crash killed all 259 people aboard and 11 people on the ground on 21 December, 1988.

Earlier, Mr Protheroe held up a model of the jumbo jet, with red, green and yellow patches showing how the plane had disintegrated in mid-air.

Relatives of the victims and the defendants watched as he used the model and diagrams to illustrate the catastrophic effects of the explosion.

The defence want the container brought to court

He described how the blast initially blew a 20 by 20 inch (50 cm) hole in the fuselage and created further "starburst fractures" and "petalling" of the plane's metal skin from the subsequent explosion of hot gases.

AAIB photographs produced in court of a partial three- dimensional reconstruction of the smashed plane showed clear evidence, Mr Protheroe said, of a "shatter zone" in the left front cargo bay almost directly under the second "A" in the Pan Am logo on the side of the jet's giant forward cabin.

The trial was adjourned again, this time to allow a baggage container from the aircraft to be brought into court.

Air accident investigators have reconstructed the metal container, which is too big to be brought through the courtroom doors.

It may have to be taken apart and rebuilt again in front of the three judges in a process which could take a whole day.