GSR particles deposited on the hands as a result of firing are not stuck there by some 'magic' glue-like property. Neither are they imbedded in the skin. They are merely lying on the surface of the skin. They are, therefore, readily removed by everyday activities.
If there is anything in their favour for being retained on the surface of the skin, it is their exceedingly small size. Being in the range of 0.1-5 | (1 | = 1 X 10-6 meters), they readily become trapped in the microscopic folds of the skin or drop down into hair follicles. Even so, for all practical purposes, all GSR particles will be removed from the hands by everyday activities within 3 hours or, at the very most, 4 hours of a weapon being fired.
Washing the hands will immediately remove all the GSR particles. Great care should also be taken if a suspect requests to be allowed to go to the toilet as urine is also very effective at removing GSR particles.
Likewise, if the suspect requires medical treatment and is covered in a rough hospital blanket, the GSR particles will also be immediately removed.
Insertion of drips into the back of the hand by the hospital should also be discouraged as the insertion point is usually scrubbed with a disinfectant. The medical profession are usually more than willing to assist, and other sites for drip needles are easily located.
If it is raining or the suspect is sweating heavily at the time of firing, the result will, once again, be negative.
In the case of a deceased person, the problem of removal of GSR particles by everyday activities is not relevant. Assuming the GSR particles are not removed by some external means, they should remain on the hands of the deceased indefinitely. If, however, the body had been placed in the mortuary refrigerator, the skin does become clammy and it is very difficult to take the samples. If possible, it is preferable to take the GSR tapings from the body at the scene.
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