Properties of Firearm Discharge Residue

The development of the particle analysis method for FDR detection and identification involved consideration of how the particles are formed and of their physical and chemical nature.170,171 

At the present time the exact mechanism(s) of formation of the particles can only be deduced from considerable practical experience and limited experimental work, most of which, if not all, has been concerned with the elemental content of FDR particles. 

Detectable FDR is mostly particulate in nature. Unjacketed lead bullets produce residue in which greater than 70% of the particles are lead. Coated bullets give the same result, except that a substantial proportion of the lead particles contain copper from the coating material. With jacketed or semi-jacketed bullets the proportion of lead particles in the residue is greatly reduced. It was concluded that most of the lead in the residue comes from the bullet rather than from the primer. This has subsequently been confirmed by experiments involving the use of radioactive tracers.172 

The stability of the smaller lead particles under the SEM electron beam suggests that they consist of metallic lead rather than lead oxides. Considering that most of the lead particles originate from the bullet, coupled with their stability under the electron beam, leads to the conclusion that the vast majority consist of metallic lead. 

Particles due to the discharge of a firearm can be loosely divided into two types those originating from the bullet, and those originating from the primer. This is a broad general classification only and is not absolute. Particles classified as primer particles because of their elemental content are 

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