It seems to me that Al Megrahi’s prosecution was ‘not proven beyond reasonable doubt.’ and some of it was fabricated for political reasons. In fact his personal conviction was mainly based on a single identification.
Fragments of a Samsonite suitcase believed to have contained the bomb were found. Items of baby clothing, thought to have come from the same suitcase were traced to a Maltese merchant who testified that he sold the clothes to someone of Libyan appearance which he later identified as Al-Megrahi. However, he had seen a picture of Al-Megrahi in a magazine beforehand.
Whilst this identification is important, the possibility of corruption has to be considered in view of the following.
A circuit board fragment was found embedded in a piece of charred material. These pieces were thought to be part of the bomb timer, and were identified as part of a Toshiba Bombeat radio cassette player. The timer allegedly was traced through its Swiss manufacturer, Mebo. Mebo's owner later revealed that in 1991 he had declined an offer from the FBI of $4 million to testify that the timer fragment was part of a timer supplied to Libya. The Mebo employee who appeared in court lied and later admitted that he had stolen a timer printed circuit board from Mebo and gave it without permission to "an official person investigating the Lockerbie case"
A former FBI laboratory scientist described the FBI laboratory itself as a "crime scene", where an unqualified colleague would routinely alter his scientific reports. The interviews also revealed that the timer fragment had never been tested for explosives residue due to "budgetary reasons".
In addition, an unaccompanied bag had been routed onto the flight, which was shown to be the suitcase that contained the bomb and a security guard had reported that Heathrow's Pan Am baggage area had been broken into 17 hours before flight 103 took off. Police lost the report and it was never investigated or brought up at trial.