Evaluation of Exhibits From a Murder Case Using the Lead Isotope Method and Scanning Electron Microscopy

• NCJ Number: 197324
• Journal: Journal of Forensic Sciences Volume: 47 Issue: 5 Dated: September 2002 Pages: 1015-1021
• Author(s): Brian L. Gulson Ph.D.; John C. Eames B.Sc.; Jeffrey D. Davis B.Sc.
• Date Published: September 2002
• Length: 7 pages
• Publication Format: Article
• Publication Type: Report (Study/Research)
• Language: English
• Country: United States of America

Annotation

This research used a combination of lead isotopes and scanning electron microscopy to determine the relationships between various exhibits in a murder case.

Abstract

Samples included lead projectiles removed from the deceased's head and a pillow, lead-rich scrapings and particles (gunshot residues) from spent cartridges and a silencer, and particles from a pillowcase. A re-evaluation of these exhibits was conducted by using the lead isotope fingerprinting method in combination with scanning electron microscopy/energy dispersive spectrometry (SEM/EDS) to determine the geological, and hence potentially the manufacturing, source of lead in selected exhibits from the murder case. The analysis found that the lead projectiles had the same isotopic composition, with the lead being derived from the same dominantly geologically old sources. The lead smear from the silencer had the same isotopic composition as the projectiles, and the lead was probably from the same source. The particles from the spent cartridges had varying elemental compositions, which ranged from PbO to PbCuZn Ba with or without Si, and they were consistent with derivation from the primer. The lead isotopic compositions of the particles from the spent cartridges showed some variations, but these were markedly different from those of the projectiles, indicating lead from a mixture of geologically old and geologically young lead. The particles from the pillowcase were very small and showed varying isotopic compositions, some consistent with the gunshot residue from the cartridges. Since the exhibits had been handled extensively prior to the current investigation, there was a high likelihood that handling was not done in clean room environments and may have been contaminated, making the results of the analysis useless as evidence. Nevertheless, a combination of high-precision lead isotope measurements with scanning electron microscopy provides a powerful tool for forensic investigations, provided that precautions are taken in handling the exhibits. 3 figures, 1 table, and 11 references