Brass cases - it is relatively easy to pick up rounds without actually touching any lead at all. Easier still to load such rounds into the ammunition magazine of a rifle like the Pargeter rifle, or the Bamber rifle, without touching any lead component part of a .22 round...
What amazes me - is why no one commissioned tests to see if it was possible for someone like Sheila to pick up indivual rounds and load them into the ammunition magazine, from rounds tipped out of a box onto a worktop, without any trace of lead at all being transferred from the brass bullet cases onto Sheila' s Hands? I suspect that if such tests had been done, or even at this late stage get done, it will give a far better insight into whether or not it was possible for Sheila to have handled bullets at all...
Tests carried out by prosecution volunteers to pick up bullets and load them into the magazine of the rifle, involved such volunteers picking up individual rounds by the lead part of the rounds in question, and whilst loading them into the guns ammunition magazine, these were pressed/forced in by exerting the fingers on the exposed lead part of the bullet...
Bearing this in mind, you would expect to find traces of lead upon the hands and fingers of the volunteer who undertook or performed such tests in that/this manner - but imagine if that same volunteer had been instructed to pick up individual rounds without any contact at all with the lead part of a/the round, and load each one into the ammuniwion magazine of the same gun without touching any lead of/in the round, so that bullets were only loaded and pressed into position inside the ammunition magazine, only touching the brass caes, or brass lip/rim of each round, you would get a totally different set of results than those obtained, and what is more, these different results would be in keeping eith the very low levels of lead actually found upon the swabs taken from Sheila's hands...