title: Lead isotope ratios for bullets, a descriptive approach for investigative purposes and a new method for sampling of bullet lead.
abstract: To establish a link between a bullet fired from a suspected firearm, investigation of striation marks are one of the corner stones in the forensic laboratory. Nevertheless, on some occasions, the bullet may be deformed to such extent that traditional investigation of striation marks will be impossible. Fragments of lead can be investigated by lead isotope ratio determination in order to distinguish between bullets with different origin. This approach initially seems reasonable, since the abundance of lead isotopes varies significantly in nature. To make a method valid for forensic purposes, it is important to have a fundamental understanding of the variation within a box of lead bullets and the expected variation between boxes. Studies of variability within and between boxes of ammunition are imperative to perform any type of forensic interpretation, both in an investigative and evaluative context. This work presents an extensive study of variability within and between boxes of ammunition by use of multicollector inductive coupled mass spectrometry. As a first approximation to classify bullets to any given source, a simple and robust graphical method is presented. In addition, an easy-to-use sampling procedure of lead is presented.
authors.affiliation: National Criminal Investigation Service (KRIPOS), P.O. Box 8163, Dep, 0034 Oslo, Norway; University of Oslo, Department of Geosciences, P.O. Box 1047, Blindern, 0316 Oslo, Norway. Electronic address: knutesj@geo.uio.no.
authors.forename: Knut-Endre
authors.initials: KE
authors.lastname: Sjåstad
authors.affiliation: University of Oslo, Department of Geosciences, P.O. Box 1047, Blindern, 0316 Oslo, Norway.
authors.forename: Siri Lene
authors.initials: SL
authors.lastname: Simonsen
authors.affiliation: University of Oslo, Department of Geosciences, P.O. Box 1047, Blindern, 0316 Oslo, Norway.
authors.forename: Tom H
authors.initials: TH
authors.lastname: Andersen
keywords: Bullets; Collection of lead by swabbing; Lead isotope ratios; Lead isotopic composition (LIC); Multicollector inductive coupled plasma mass spectrometry (MC-ICP-MS)