Tests avoided by the police, authorities, and the experts - the cover up...
There were two things which could have been done in time for the 2002 appeal which were ignored, (1) checked for dna of Sheila's on the flat surface on the end of the rifle (18), and (2) check the flat surface on the top end of the silencer, for a presence of Sheila Caffells dna? Since, if the silencer was fitted to the guns barrel at the time she received or sustained the fatal shot beneath the chin, her dna would almost certainly have been present on the end of the silencer, or the barrel of the gun, because it supposedly was thrust into position against the underside of her chin at the time the fatal shot was fired...
None was found - which tells its own story...