D Kimberley Molina 1, Michael Martinez, James Garcia, Vincent J M DiMaio: explained in 2007 for "experts" the likelihood of GSR being on deceased person's hands who shot themselves. Some of the best in the world listed there.
If I recall the attorney acting name correctly as Ashby, he will be well aware of that paper and also another published paper which in part dealt with the suicide of Robin Bain after skeptics had tittered on for years about the impossibility of Robin Bain shooting himself because he "couldn't" reach the trigger - only to see it demonstrated at trial.
If there is any evidence of GSR on Sheila's clothing that would still be consistent with suicide, though unfortunately I doubt investigating police had much of a clue about it and possibly no tests were done.
There are 2 tricks for novices to this case, take a broom stick put a nail in it at the correct distance from one end lie on the floor and see with the rifle (to the left from memory depending on the which side the wounds were on, with the right hand on the "barrel" and the left reaching to the trigger. Having absorbed that and using the same length model swing it overhead into a lower recessed wall and find that the height of the arc does not allow a "scratch" to be made right from the edge.
Lastly dig out mike g's now famous reconstruction of the stairs to help understand the evidence that shows Nevil was turned away on the stairs.
I have every confidence that the Bamber case may finally crack this time not least because of the counsel acting and his experience in MOJs, but also because forensic science around suicides is far better now (the paper below is 2007). Any withheld evidence that favours Jeremy re the phone calls and any activity in the house after the cordons were in place increases the chances of success along with the science once rejected by either the CCRC or COA, and now expanded upon by 30 years of progress in that area.
As a matter of interest one of the co-authors in the later published paper mentioned above, an English woman living in NZ at the time was somewhat stunned when on a online forum running at the time in NZ I invited participants to do the standing with left foot on a chair routine, rifle barrel in right hand, head tilted left and finger on the left hand easily able to reach the trigger as a demonstration of Robin's ability to have shot himself. Anyway she accomplished a rare feat in co-authoring a paper with Vincent.
The first time I met Joe Karam (after the acquittal of David Bain) when he came to the house an immediate question was where was my broom. I actually had brought a length of 1" dowel which I cut to the right length then put a nail positioned as the trigger at the right measure. As that was a case where the silencer was still on the barrel much to the chortles of the sceptics.
Some years after DB's acquittal a NZ man who was a scientist David Giles blew up crime scene photos of Robin's hands and saw what appeared to GSR. The GSR was in a arc consistent with a curve in the magazine and consistent with loading with a thumb. The very good forensic pathologist in that case who said the famous words regarding evidence which he recorded "if it was there it is in the report" or similar, said after the trial that the alleged GSR mark was not present at autopsy which was some 14 hours or so after TOD.
Ashby will have gone over the autopsy reports and found them wanting. Immediate attention to core body temperatures of the deceased and ambient temperature may in the fullness of time, if the conviction is quashed show, that Jeremy would never have been charged if proper crime scene protocols were followed - like get the FP inside as quickly as possible and plod out.
Lastly on the normal police/Crown waffle about all the processes that the case had been through and upheld, a reminder that one of NZ's most significant MOJs followed 2 trials with guilty verdicts and had the old "re-searches" that found evidence a bullet case that had not been manufactured at the time of the murders.
I would be not be surprised if the English woman I mentioned above had not been approached to help the defence in Bamber - she's got the creds.
Robin Bain could not have shot himself and either could have Sheila. Sure.
https://pubmed.ncbi.nlm.nih.gov/17721163/
"Since only 50% of cases where the person is known to have fired a weapon immediately prior to death were positive for GSR by SEM-EDX, this test should not be relied upon to determine whether a deceased individual has discharged a firearm. Furthermore, in only 18% of cases was a discernible pattern present indicating how the firearm was held. The low sensitivity, along with the low percentage of cases with a discernible pattern, limits the usefulness of GSR test results by SEM-EDX in differentiating self-inflicted from non-self-inflicted wounds."