I totally agree with Puggy. Had Sheila used the rifle her fingerprints would be the primary ones on it and all over it. Any fingerprint expert can tell which print is the older print when two prints overlap.
We know the rifle was used to beat Nevill around the head so there should have been many prints all over it but there weren't. The only explanation for this would be either the perp wore gloves or the rifle was wiped clean before new prints were applied.
Absolutely, John.
It’s patently obvious that in the violent struggle over the rifle between Jeremy and Nevill, one of his gloves would so easily have fallen off. And that’s why he had no option but to wipe the whole rifle clean of all fingerprints as it would have shown Jeremy’s prints overlapping Nevill’s.
That could have been why he was so enraged even after Nevill was dead, and kicked and smashed his dead body about — he was furious he’d had to clean the prints off.