By BBC Scotland's legal affairs correspondent Reevel Alderson
The criminal investigation into the Lockerbie bombing required luck before an incredible forensic investigation could begin to point the finger of suspicion at Megrahi and ultimately Fhimah.
First, a baggage handler in Frankfurt from where a feeder flight had left to join Pan Am 103, realised the West German airport could possibly have been involved.
She printed off computer records of all the baggage which passed through the airport on December 21, 1988 - a record which otherwise may have been purged from the computer.
A circuit board fragment which was initially thought to be rubbish
It subsequently proved the prosecution claim that an unaccompanied bag went from Malta onto the Pan Am feeder flight.
The forensic examination also relied on initial luck, or the thorough searching of the debris trail, stretching 100 miles east of Lockerbie.
This set off a series of events resulting in the indictment against the two Libyans.
January 1989: A piece of charred grey shirt is found in a field near Newcastleton. Along with many other pieces of debris, it is transferred to a central store, its significance unknown. Only later is it discovered that wrapped within it is a fingernail-sized piece of circuit board with a tell-tale identifying mark - the number one.
13 January, 1989: A fragment of circuit board is found in the Longtown store. It is wedged in the identity plate of a baggage container, bent double by the force of the blast. At first it is thought it is a piece of rubbish.
April 1989: The fragment, along with others recovered, is identified as being from a radio cassette player, one of a range of six Toshiba twin speaker models.
1 September, 1989: Enquiries begin in Malta after the shirt fragment is identified as having been made there. Detectives visit the Yorkie Clothing Company and also Mary's House, a small clothes shop, owned by Tony Gauci. Yorkie had made trousers found near the shirt fragment - one of only two pairs made.
Tony Gauci provided information for an artist's impression
13 September, 1989: Gauci provides information for an artist's impression and photofit picture of the Libyan man who bought clothes from him.
June 1990: The piece of electronic timer circuit board embedded in the shirt fragment found near Newcastleton is positively identified as part of an MST-13 timer. The shirt was found alongside pieces of speaker from the radio cassette player and - crucially - pieces of the instruction manual for the player. This proved the bomb had been in the cassette player.
Summer and autumn 1990: Police visit Togo and Senegal to inspect MST-13 timers, one seized by the CIA from Libyans.
September 1990: First interviews with Mebo of Zurich, manufacturer of the timer, provide information linking the company with Libya.
15 February, 1991: Mr Gauci identifies Megrahi from a police photospread as the man who bought the clothes in his shop.
Baggage tags helped complete the evidence chain
April 1991: Fhimah's diary is found in an office in Malta. It has entries linking Fhimah to Megrahi and, crucially, to the collection of airline baggage tags which would have been vital to enable an unaccompanied bag to be taken from Luqa Airport. At the same time Scottish detectives checking Maltese immigration records track Megrahi's visits to the island, and that he stayed the night before the bombing in a hotel room. From there, hotel records show he made an early morning call to Fhimah's flat.
14 November, 1991: Warrants are issued for the arrest of Megrahi and Fhimah.
13 April, 1999: Tony Gauci again identifies Megrahi, this time in an Identification Parade at Camp Zeist.