It requires years of experience and examination of hundreds of cases to competently review and interpret the GSR findings in the full range of criminal cases involving guns.  All of the methods used should be accredited and stand up to scrutiny and full anti-contamination measures should be in place.  The interpretation of what constitutes a GSR particle is not undertaken to the same standard in all laboratories and this is based on the level of expertise of the scientist.  The findings should also be subject to a full interpretation based on the case circumstances and any other relevant information that could have a bearing on the presence of GSR.  This is particularly important in cases where only single particles or low levels of GSR are found or where there is a possibility of cross-contamination. FFC offers this expertise.