by Dr Morag Kerr

Published iScot February 2015 Edition

WHEN Pan Am 103 blew apart in the sky over Lockerbie on December 21 1989 a 90 mph westerly gale blowing.

The wind spread falling debris from the disintegrating Boeing 747 on route to New York from London across the Dumfriesshire countryside. It was sorted by weight and air resistance resulting in two distinct “debris trails” of aircraft parts. Most of the lighter luggage contents were found in a continuation of the southerly trail while papers and letters made it as far as the Northumberland coast, and some were lost to the North Sea.

The result was the early stages of the investigation resembled a giant litter-picking operation. “If it isn’t growing, or a rock, pick it up” was the instruction to members of the investigation team tasked with retrieving every scrap of evidence.


As soon as the first pieces of the blast-damaged baggage container were brought in on Christmas Eve the police knew they were dealing with the mass murder of 270 people. Every item of debris recovered, down to the smallest rag or scrap of suitcase, was logged with the precise location where it had been found.

One item designated PI/995, became a crucial clue and a nexus for numerous conspiracy theories. It was logged as being picked up near Newcastleton, 20 miles east of Lockerbie, on 13th January 1989. Much has been written about the provenance of this item, a scrap of shirt collar burned by close proximity to the explosion.  Particular attention has focussed on the scanty and problematic documentation of its most significant feature – a 1 cm square fragment of fibreglass printed circuit board found embedded in the cloth and dubbed PT/35b.

This fragment is at the centre of a confused and confusing mess of renumbered pages, inconsistent dates and general muddle which have led many people to speculate that it was actually a retrospective plant.

These suspicions are heightened by the absence of any record during 1989 of a serious forensic investigation of the item. While scientists at the Royal Armament Research and Development Establishment (RARDE) were obsessing over other pieces of circuit board at that time PT/35b sat apparently overlooked in a side-room.

Despite theories to the contrary, detailed examination of the documentation doesn’t prove it was inserted retrospectively. The visual match with the MEBO boards was perfect, right down to an

oddity in the tracking caused by the Letraset of the template not having been cut quite flush. One thing seems reasonably certain. The scrap of collar and the shirt it was part of was extremely close to the explosion.

The careful logging of the recovered debris shows four separate parts of that same shirt recovered from widely separated locations which form an almost perfect straight-line continuation of the “southern debris trail”.

This all fits perfectly with the known distribution of the falling, wind-swept debris.

Was PT/35b, the infamous printed circuit board fragment, actually lodged in the cloth at that time? It’s impossible to say, but it has not been proved it wasn’t. What has been proved is something altogether different, something entirely unsuspected during the years when the defence teams were poring over the forensic notes and wondering if certain pages might have been added at a later date.

Serious attempts to find out what the fragment PT/35b was began in earnest after it was handed over to Scottish detectives in January 1990.

Physical and chemical analysis carried out at the University of Strathclyde, while policemen patiently telephoned and visited manufacturers of electronic components and suppliers of raw materials, found nothing earth-shattering.The raw materials were unremarkable, used in millions of gadgets and gizmos worldwide.

However, a detailed report dated September 1990 cataloguing the effort noted one particular feature that seemed anomalous. Printed circuit boards have a coating on the circuitry, known as ‘tinning’, applied to make the


Fragment PT/35b

components easier to solder. In mass manufacturing this coating is almost

always a tin/lead alloy, however PT/35b had a coating of pure tin. It had been applied in such a way as to suggest this had been done by electroless plating, a method used by amateurs making only a few boards as a hobby.


Timer – MST-13 made by a Swiss firm called MEBO

The origins of PT/35b remained elusive until, in June 1990, Scottish police allowed the FBI to become involved.

With the help of a CIA agent, the fragment was matched visually to a circuit board from an electronic timer known as an MST-13 made by a Swiss firm called MEBO. Inquiries in Switzerland revealed only 20 of these timers had been produced as a special order for the Libyan armed forces.

This was a major breakthrough in the investigation and the cause of the switch in direction from Iran and the PFLP-GC to Gaddfi’s Libya as the prime suspects. It also provided the perfect answer to a conundrum that had plagued investigators since early 1989.

How had one of the PFLP-GC’s devices travelled on three flights before blowing up, when the triggers usually used by that group were altitude-sensitive? The MEBO devices were count-down timers capable of being set to go off days in advance, irrespective of altitude.

The Lockerbie investigators set off to hunt Libyans, and apparently never looked back.

More tests were carried out by forensic scientists at RARDE,  overseen by Allen Feraday.  His notes dated  August 1, 1991 record the same findings as the tests done in Scotland the previous year. The coating on the circuitry was pure tin.

However, there was a complication. Investigators had samples of the MEBO-produced boards for comparison and they were not the same. They had the usual alloy coating seen on mass-manufactured products and therefore different to PT/35b. The matching of PT/35b to the unique batch of timers supplied to Libya was central to the prosecution of Abdelbaset al-Megrahi and Lamin Fhimah in 2000-01.

With the timer off the table, proof that Lockerbie was a Libyan operation would have been absent, and the prosecution would have been in all sorts of trouble. 

The metallurgy discrepancy was put to one side. Mr. Feraday’s original notes were not disclosed to the defence and the matter was covered by having him read out relevant section of his fair-copy report written some months later. In that, there was no mention of any discrepancy.

The report read “… it has been conclusively established that the fragment materials and tracking pattern are similar in all respects to the area around the connection pad for the output relay of the ‘MST-13’ timer.”
But, it wasn’t similar in ALL respects..

None of the independent scientists who carried out testing on the fragment were called to give evidence. The matter wasn’t brought up with the production manager from the company which had made the boards for the MST-13 timers. The fact the composition of the coating showed that PT/35b had been made by a completely different process from the MEBO instruments was never highlighted.

Further investigation carried out by Megrahi’s defence team in preparation for his second appeal revealed the company which made the PCBs for the MST-13 timers had never used an electroless plating technique. All the instruments supplied to Libya by MEBO had the usual lead-alloy coating on the circuitry.

Corner of PT/35b compared to a genuine MST-13 board and the original template

Corner of PT/35b compared to a genuine MST-13 board and the original template

PT/35b could not have come from a timer sold to the Libyan armed forces as claimed by the prosecution.

The visual match between the fragment and the boards from the MEBO timers is striking, indicating that they all originated from the same template.

In most other respects the match is perfect, in particular the use of nine-ply fibreglass (when eight-ply is more common) and the presence of a green solder resist coating on the reverse of the board only, when the usual place for such a coating would be on the business side. PT/35b is an odd mix of professional and amateur construction. It looks like a deliberate copy of an MST-13 circuit board, but with just that one tiny discrepancy – possibly due to it being a one-off item made without access to a manufacturing production line.

A few other points can be clarified. Despite allegations to the contrary PT/35b can be seen to be the same item all through its history.

Nobody switched it for something else during the investigation. It probably went to America at least once, but it was accompanied by an officer of the Dumfries and Galloway Constabulary during that time, so it didn’t leave the control of the Scottish police. Most of the brouhaha surrounding its provenance is unfounded, or at least unproven.

Who made it, and why? Did it fall out of the sky that December night, or was it somehow added to the rest of the debris recovered from the shirt collar at a later date, its dodgy provenance concealed behind the smokescreen of the disorganised forensics notes? If we knew any of that, we might be a lot closer to solving the mystery of the Lockerbie bombing, still impenetrable after more than a quarter of a century.

*Dr Morag Kerr is author of the book ‘Adequately Explained by Stupidity? – Lockerbie, Luggage and Lies’.

read on > LOCKERBIE – Scene of the crime

*Dr Morag Kerr is the author of the book ‘Adequately Explained by Stupidity? – Lockerbie, luggage and Lies’