SC's hands were swabbed for the presence of GSR using a kit designed for this very purpose but apparently EP sent to the lab with an unrelated firearm and on this basis the swabs were rejected on grounds of potential contamination. But even if this hadn't happened the test was flawed for many reasons including what you've stated above.
There are no other reliable tests used to determine whether someone has recently discharged a firearm. Tests for bullet lubricant, which you refer to above as wax, and gun oil are not valid scientific tests. If others disagree please identify one of the many UK forensic service providers who offer such tests.
The above will form additional points for the 3rd appeal.
Please note I said additional and not the main contenders.
The forensic scientists knew what they were doing Holly.
If you read the article I linked above, a test for GSR is only useful in determining if someone has fired a gun if they are not at the scene as basically GSR goes everywhere. On the shooter, on the victim, on surfaces and it can be easily transferred. Testing JB might have been useful, but not conclusive. It's actually a very limited piece of science.
Yes, the lab first rejected the swabs on the grounds of possible contamination which of course, JB tried to turn into yet another conspiracy. The CoA had to point out that any contamination would have only worked in his favour. The results of these tests showed only low levels of lead which were not consistent with
loading the gun.
From the Appeal, point 177:
At trial Brian Elliott, a scientist from the Home Office Forensic Science Laboratory, gave evidence that the item DRH/33 described as "Swabbing Kit – hands of Sheila Caffell" had been received at the laboratory on 13 September 1985. He said that tests had been carried out for the presence of lead and that only "very low levels of lead have been detected on the two hand swabs". He further reported that tests had been carried out on two members of the laboratory staff who had loaded eighteen cartridges, similar to those used to shoot those who died at White House Farm, into the magazine of the rifle, and "significantly higher levels of lead" had been detected. Clearly if this evidence was right it cast doubt upon Sheila Caffell having loaded the cartridges into the gun and thus to her having killed the others and then herself.Point 187:
"The hands – were swabbed – swabs rejected by the laboratory. Later raised by D/Superintendent Ainsley in conference at the laboratory when the laboratory again stated that it was too costly to do and that it would be expected to show a positive result as the body of Sheila was in a room contaminated by gunfire. D/Superintendent Ainsley made issue that the swabs should be examined and if not done he wished a statement to explain why it had not been done. As a result they were examined and found to be virtually negative of residue, i.e. lead, oil and propellant."
