TIME SINCE DISCHARGE OF SHOTGUNS

A method for estimation of the time since the latest discharge of a sh otgun is presented. This method is based on SPME (Solid Phase Micro-Ex traction) sampling from the atmosphere inside the shotgun barrel. Two analytical systems were used in parallel, the GC/TEA and GC/FID(MS) sy stem. These two systems detect various combustion products and the est imation of time since the latest discharge is based on the rate of esc ape of the volatile discharge residues from the barrel as a function o f time. If the ammunition used in the suspect firearm is known, the us e of decay curves for the actual firearm and the actual ammunition is fairly straightforward. For unknown ammunition, repetitive samplings m ust be performed and the results fitted to decay curves obtained for o ther ammunition types according to the proposed procedure. Generally, the method presented in this study can give an indication whether a we apon was fired, e.g., 2 to 3 days, 1 to 2 weeks, or more than 3 weeks ago. Some factors that may impact data interpretation were studied, su ch as the effect of cleaning the barrel, the number of shots fired, th e eventual disturbance to the system by SPME sampling and the effect o f temperature of the storage.