A scientific analysis of the Crown's discredited theory that approximately 1lb of semtex contained in a Toshiba radio caused the destruction of Pan Am 103 over Lockerbie, has concluded that the notion is "scientifically implausible."

The report, by Dr Ludwig de Braeckeleer agrees with the findings of John H Parkes, a former MOD contractor and explosives engineer who assisted in the rescue operations in Lockerbie, and subsequently submitted a report of his findings to the then Scottish Secretary Malcolm Rifkind. Parkes was never called as a witness to the trial.

Dr de Braeckeleer's findings reiterate the initial findings from US sources, that the Crown theory does not stand up to forensic scrutiny. 

"In the immediate aftermath of the tragedy, researchers at the Centre of Explosives Technology Research in Socorro, New Mexico, estimated that up to thirty pounds of explosive was needed to destroy a Boeing 747, if the explosion had occured in the container. We agree with that estimate," the report says.

"As the explosion of one pound of Semtex H inside the luggage container does not generate a blast wave sufficiently powerful to fracture the skin of the fuselage, we have little choice but to conclude that the verdict appears scientifically very implausible."

The AAIB report into the destruction of the Boeing 747, which concluded that the plane was downed by a small semtex blast, contains five conflicting accounts of the moment of the explosion on board the aircraft.

Evidence of fragmentation observed on victims at the site and on the wreckage - which was not heard at the trial- indicate an explosives "signature" that was not consistent with a semtex blast close to the skin of the fuselage. Unbroadcast footage of the wreckage, and contemporaneous photographs of the crashed plane, shows puncture damage to parts of the plane far away from the claimed site of a semtex blast, and of a character indicating far more powerful explosives events on board.

The evidence introduced during the trial to support the semtex theory, which was claimed to have been recovered from the crash site, was later demonstrated to have actually come from simulated test explosions.

The Firm's investigation, conducted over three years and which concluded that there was sufficient evidence to justify an investigation into the possibility that the airliner was downed by a larger explosion, possibly caused by the illegal carriage of munitions on board, can be read here. 

In 2004, it was revealed that Soviet munitions were carried illegally on civilian passenger vehicles, including the MV Estonia, which later sunk in the Baltic sea with the loss of 852 lives.

The report's conclusions can be read here.

This morning, a Crown Office spokesman said: 'Since the case is live and currently before the appeal court, it would be wholly inappropriate to comment on any speculation or indeed, any aspect of the case.'