The Chronology of PT/35(b): 2 March 1990

2 March 1990

Metallurgy test and report. No samples removed

Williamson and Harrower attended the Bio-Engineering Dept of Strathclyde
University by previous arrangement and met with Dr Rosemary Wilkinson (S5579)
(Whitehead in his defence precognition said he recalled suggesting to the officers that
they try Strathclyde Uni; in her defence and Crown precognitions Dr Wilkinson said
the officers arrived out of the blue, but might have been referred to her by her
superior), to gain more information about the silver coloured metal that overlaid the
copper conducting tracks and land on the fragment.

In her HOLMES statement Wilkinson states that she examined the metallic areas of
the fragment microscopically and found that the two parallel bars showed the presence
of copper and tin and in some places only copper, which would be consistent with the
parallel tracks having originally been coated in tin but some of the tin subsequently
having been removed.

She stated that on the pad (the “1” skape) she found copper, tin and lead, which would
be consistent with a layer of solder having been overlayed to the previous structure of
copper coated by tin. She found some areas of the land to have little or no lead,
suggesting either that the solder had been melted, uncovering these regions, or that
solder was applied manually to the pad but not to the regions where there was little or
no lead. She provided metallurgy printout data which was designated DP/21 (prod
343) and 7 photographs produced in her test machinery, designated DP/20 (prod 344),
the police label for which Harrower in his ch10 CP noted had not been signed by
Wilkinson, but he could not offer any explanation as to why. According to
Williamson’s memo of 16 March 1990, Dr Wilkinson also stated that she saw at the
bottom left hand corner of the pad a lead rich area with a diagonal marking that
appeared to be a section of a cylinder, which she said could possibly be the remnant
of where wire was embedded in the solder.

DP/20: Photo 6

DP/20: Photo 6

In his memo to the SIO of 16 March 1990, Williamson states that the fact that it was
only tin as opposed to tin/lead that coated the tracks was, without exception, regarded
by all the experts they visited as being the most interesting feature, as it was unusual.

The memo states that in furtherance of this information an examination was carried
out to establish the thickness of the tin. This was done by Digital Equipment
(Scotland) Limited using Fischer scope XRF and measurements were taken at various
points, which showed the tin varied in depth from 1.41 microns to 4.57 microns.

There is no further information about this test, the date it was done or about who
carried it out. The memo also states that enquiries were made with numerous
companies in the UK in an effort to learn more on the use of tin in these
circumstances but the enquiries proved negative, there being no companies known in
the UK who continue to use pure tin in the way that it had been applied to PT/35(b).
Again, there are no further details about these enquiries in the memo.

In her defence precognition Dr Wilkinson mentioned having done various
examinations including x-ray examinations. She suggested that the officers seemed to
want to know whether the fragment had been involved in an explosion, and her
opinion was that, while she noticed some changes to the metal, she did not find
anything that would specifically indicate it was involved in an explosion e.g.
abrasions to the surface of the metal parts or loss by melting. She could not say for
certain whether or not it had been in an explosion. She was precognosced a second
time by the defence on 1 June 2000, apparently because of her comments about the
absence of evidence of explosion damage, and she went into greater details about the
various tests she conducted. There are also papers in the McGrigors files in which the
possibility is discussed of calling Dr Wilkinson for the defence, given her position
that there was no evidence to confirm an explosion. However, it was agreed that she
accepted she lacked expertise in this area (i.e. in explosion damage and in PCBs), and
it was agreed that she should not be called as a witness. In her CP she stated that the
test of one the copper tracks revealed a high ratio of copper and no lead, and that on
the land, there was no consistency in the ratios of copper, tin and lead in the five areas
tested. She later stated that she would expect to see these three elements on the land,
as it would be consistent with a layer of solder being overlayed on a copper base, but
she would expect the ratios to be fairly uniform when produced by the manufacturer,
whereas on the fragment certain areas showed little or no lead at all. She suggested
this could be due to errors in manual application of solder or partial melting of the
solder, uncovering the copper below.

NB Dr Wilkinson was also seen by police in 1992 and asked to examine a control
sample MST-13 circuit board – see 28 Feb 1992 below. NB Wilkinson’s signature is
visible on the label for PT/35(b).

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