Because she didn't do anything to get them dirty?
Also the ballistics expert (Malcolm Fletcher) states in his report that Sheila's night dress would have firearms residue on it if she fired the suicide shots, why isn't there any?
It appears that Sheila was shot at close range, the gun by her side, therefore this suggests that she would have had residue on her skin and her clothing.
Note that her hand swabs were not tested till the 17th September, which could mean that the residue had diminished.
