Plumbum Microraptus: Definitive Microscopic Indicators of a Bullet Hole in a Synthetic Fabric
Palenik, C.S., Palenik, S., and Diaczuk, P. (2013) Plumbum Microraptus: Definitive Microscopic Indicators
of a Bullet Hole in a Synthetic Fabric. Microscope (2nd Quarter) 61:2 51-60.
Published on: 8/1/2013
A central question in a criminal forensic investigation involved a hole (later termed a “defect”) observed in a garment and whether it was produced by a bullet or some other means. The individual wearing the item was known to have fired or been in the vicinity of a firearm that was discharged, rendering the presence or absence of gunshot residue on the garment irrelevant. The micromorphology and elemental composition of the severed fiber ends in a series of exemplar bullet holes were characterized to identify specific physical indicators of the bullet-garment interaction on a microscopic scale. This study confirms prior research indicating that fiber failure, due to the high energy transfer from a bullet to a synthetic fabric, is consistent with a high-speed tensile fracture mechanism, which results in characteristic fiber-end micromorphology due to partial melting. In addition, scanning electron microscopy (SEM) imaging and elemental analyses by energy-dispersive X-ray spectroscopy (EDS) provide direct evidence of the capture of detectable microscopic lead particles both on and within the melted fiber ends, a process termed here as plumbum microraptus (microscopic lead capture).
These lead particles are observed primarily as planar abrasion fragments but also as spherical particles, the latter of which further illustrates the high- energy transfer. Through the study of individual broken fibers from within a suspected bullet hole, these characteristic indicators provide a minimally invasive and direct means to definitively associate or (equally important) dissociate a fabric defect with a bullet perforation.