Brake linings: a source of non-GSR particles containing lead,barium, and antimony

The observation of environmental particles similar in composition to gunshot residue (GSR) are not new to forensic experts and have been described in the scientific literature. In order to better define the origin of these particles, brake linings and their wear products were examined by SEM-EDX. The results obtained demonstrate that some types of brake linings contain lead, barium, and antimony and that they can represent a source of particles showing GSR-like elemental profiles. Most of these particles can be easily discriminated from primer discharge residue because of the high levels of iron or the presence of "prohibited" elements in the spectrum. However, particles with iron at minor or trace levels and lacking "prohibited" elements were also found. It is thus advisable to use caution when describing the composition of similar particles as "unique" to primer discharge residue. The strict application of a rigorous morphological criterion is also recommended.