LEAD-ISOTOPE RATIOS IN LEAD SMEARS AND BULLET FRAGMENTS AND APPLICATION IN FIREARM INVESTIGATIONS

This paper describes the use of lead isotopes ratios for an investigat ion of a homicide. Lead smears and bullet fragments recovered from a v ictim's clothing were compared with lead samples from two suspect bull ets. More than 90 bullets of the same caliber and produced by the same manufacturer as the suspect bullets were analyzed. The lead isotopic compositions were found homogeneous within individual bullets. Differe nt bullets from the same ammunition box also showed indistinguishable lead isotope ratios. Bullets from ammunition boxes produced in 27 diff erent months were analyzed. The results were compared with those obtai ned for bullets and bullet fragments from the homicide case. The high precision isotope ratio measurements could distinguish between lead fr om the homicide case and nearly all bullets from the ammunition boxes that were investigated. The isotope ratios for bullets from one of the ammunition boxes were indistinguishable from those for the homicide b ullets. Some bullets of the same caliber as the suspect bullets but pr oduced by different manufacturers were also analyzed by this technique . All these bullets showed clear differences in their lead isotope rat ios