It all depends on whether they tested her properly I should think? You've already proved to us that Taff Jones was incompetent. So since they were all in the same frame of mind then we must assume that they were all similarly slapdash about their work.
The lab tested her clothing and the hand swabs not Taff Jones. They used an electron scan microscope not a chemical test. The electron scan microscope was the suprior test available at the time the chmical test less reliable. There is nothing in the record that suggests they erred and no experts to challenge it. It is up to the defense counsel to find someone to try to challenge it or in the event a Jeremy supporter wants to then to find some scientific basis besides just "maybe they messed up".
Hair had a better chance of retaining GSR long term than skin so if much time passes between the shooting and testing a potential shooter then testing the hair should be done as well. But since she was not moving around it doens't matter the reduction from her skin would not rapidly happen from just lying dead. Moreover, GSR leaves clothing at a much reduced rate than even hair so clothing is the optimal place to find it.
In his case even moreso since the place on the rifle that discharges GSR would have been right next to her gown so we have the location and the fact the fabric reatins GSR combining together. Finding not a drop of GSR is very bad for the defense under such conditions.
Ironically on appeal the defense brought up the chance of officers contaminating the evidence which the Appeal Court scoffed at because if the police had contaminated the evidence with GSR that would result in GSR being found. That is just one of the things that shows that the appeal was very poorly thought out and constructed.
I understand that there is not much to work with but making ill conceived arguments just pisses courts off and takes attention away for the strongest arguments and makes it less likely for a court to take your claims serious.