NCJ Number
78667
Journal
Baylor Law Review Volume: 33 Issue: 2 Dated: (Spring 1981) Pages: 285-291
Date Published
1981
Length
7 pages
Annotation
This article describes current techniques for analyzing gunshot residues and discusses possible testimony that experts in this field can provide.
Abstract
In cases involving the discharge of a firearm, the forensic pathologist or investigator should have access to analysis of metallic deposits that may be on the hands, tissues, or clothing of a victim. Generally, the attorney and the court are presented with an analysis of handwashings or handwipings of the deceased by Flameless Atomic Absorption Spectrophotometry (FAAS) which allows an analyst to detrmine the presence of gunshot residue from the distribution and levels of lead, antimony, and barium. A newer method, Scanning Electron Microscopy/Energy Dispersive X-Ray (SEM/EDX), is also examined, as is the Trace Metal Detector Technique (TMDT) used occasionally by police and medical investigators to prove or disprove the assumption that metallic objects at a crime scene might have been handled by a suspect or victim. The discussion of methods for analyzing clothing and tissues focuses on the Energy Dispersive X-Ray (EDX). Excised tissue containing the bullet wound is first examined for the presence of powder and soot and then EDX is used to identify the metals in the residue. Because the relative quantity of metal identified is related to a firearm's range of discharge, the lead and other metal detected provide information as to range even when the body is decomposed. Weapons can cause powder tatooing on the skin of a person from a maximum distance of 18 inches to 4 feet, but patterns vary according to the distance. A firearms examiner can duplicate patterns by test firing the actual weapon and ammunition. The value of such evidence is illustrated by two cases where expert testimony on test firing strongly refuted the defendants' statements. The laboratory analyst can offer an opinion only on the results of his examination and analysis. Knowledge of the technical language allows the attorney to help the expert witness explain the findings in understandable terms and permits a vigorous cross examination of witnesses who embellish the scope of their testimony. The article includes 21 footnotes.