AFTE Store - Chemical Associations Between Bullets, Bullet Fragments, and Evidence Lifts in Shooting Investigations

Associations between lead fragments or lead transfers and the bullets that produced them are a significant finding in the investigation and reconstruction of certain shooting incidents. In a limited universe of candidate bullets, it may be possible to definitively exclude most bullets, or all but one candidate bullet from having left a particular fragment in a wound track or lead transfer onto a surface. Two analytical methods are employed to create a chemical signature of bullet lead: minor and trace elements by ICP-MS and lead isotopes by MC-ICP-MS. The amount of material required is many orders of magnitude less than previously used in the FBI’s method of Compositional Analysis of Bullet Lead (CABL) and the amount required does not visibly damage evidentiary exhibits. Lead isotopes more effectively discriminate between bullets and produced
traces compared with elemental ratios. Equally important, this method does not try to associate a bullet with bullets in a box of cartridges, but between a recovered bullet and fragments or lead transfers from an impact site. This fundamentally different application of chemical associations in bullet lead is well supported in literature and likely to pass Daubert or Frye challenges. The effectiveness of this method is demonstrated through two blind studies: one of the associations of fired
bullets and evidence lifts from projectile ricochet sites, and the other of associations of fired bullets with their respective bullet fragments from simulated perforating gunshot wounds.

Full Journal: AFTE Journal Vol 56 No 1 (2024)