Elemental Analysis Examinations

Elemental analysis examinations can identify and compare the chemical elemental composition of evidence, including:

• Firearm projectile lead

• Bullet jacket alloys

• Other metals, and

• Unknown substances.

Firearm Projectile Lead

Elemental analysis of the lead component of a firearm projectile is valuable when the projectile is too mutilated or lacks sufficient microscopic marks for identification with a firearm, when no firearm is recovered, or when the firearm cannot be associated with the suspect or suspects. The concentrations of selected elements in the lead portion of bullets, shot pellets, and other firearm projectiles can chemically characterize the source of the lead. Some chemical elements present in leads are intentionally specified and/or added by the ammunition manufacturer. Other chemical elements found in leads are unspecified contaminants. Differences in the concentrations of manufacturer-controlled elements and uncontrolled trace elements provide a means of differentiating among the leads of manufacturers, among the leads in individual manufacturer's production lines, and among specific batches of lead in the same production line of a manufacturer.

Bullet Jacket (Copper/Zinc) Alloys

Elemental analysis of the jacket component of firearm projectiles is valuable when the projectile has fragmented so that jacket fragments cannot physically be associated with specific bullets. This analysis is helpful in situations when there are multiple shooters and multiple types of jacketed ammunition are fired. The concentrations of copper and zinc comprising the bullet jacket serve to characterize the alloy class of the metal. Although there are a limited number of copper/zinc alloys used in the manufacture of bullet jackets, alloy classification can provide a means of differentiating among bullet jacket alloys of different manufacturers and among the bullet jacket alloys in individual manufacturer's production lines.

Other Metals

Elemental analysis and comparison of metals such as copper wire, steel, and aluminum can determine whether two metals or metallic objects came from the same source or from each other. The concentrations of selected elements in objects made of these metals can chemically characterize the source of the metal. The concentrations of several elements are controlled by the manufacturers to impart specific end-use properties to products. These manufacturer-controlled elements help to chemically characterize a metal object by placing it in an alloy class. The concentrations of trace elements are generally not controlled by the manufacturers. Differences in the concentrations of manufacturer-controlled elements and uncontrolled trace elements provide a means of differentiating among metals made by different manufacturers, among metals from different product lines of a single manufacturer, and among specific production runs of the metal from a single manufacturer.

Gunshot Residue

When a firearm is discharged, vaporous and particulate materials called gunshot residue (GSR) are expelled. Collecting GSR from a suspect shooter's hands and analyzing it for the presence of barium, antimony, and lead, which are major elemental components of most cartridge primer mixtures, provides data to associate a suspect with the recent discharge of a firearm or the handling of a contaminated firearm or ammunition component.

Makmal Forensik does not currently provide GSR examinations; however, a revised program is being field-tested. Contributors will be advised when GSR examinations are available.

Submitting Elemental Analysis Evidence

Questions concerning elemental analysis evidence should be directed to 03-9702366. Follow the Evidence Submission directions including Requesting Evidence Examinations and Packaging and Shipping Evidence.

• Ammunition components such as bullets, cartridge cases, and shotshell casings can be sent via registered mail through Pos Malaysia. Evidence should be packaged separately and identified by date, time, location, collector's name, case number, and evidence number.

• Live ammunition must be delivered by hand. Pack ammunition in a cardboard container. The shipper's certification for restricted articles must be included. The outside of the container must be labeled CARTRIDGES SMALL ARMS. The shipping papers must also include the weight in grams.

• Do not mark bullets, cartridges and cartridge cases, and shot shells and shot shell casings. The date, time, location, collector's name, case number, and evidence number should be on the container.