NCJ Number
57755
Date Published
1977
Length
18 pages
Annotation
COMPUTER TECHNIQUES ARE PRESENTED FOR ANALYZING THE SURFACE MARKINGS ON BULLETS TO IDENTIFY THOSE FIRED FROM THE SAME GUN.
Abstract
THE BACKSCATTERED ELECTRON SIGNAL OF A SCANNING ELECTRON MICROSCOPE IS USED TO FORM IMAGES OF SMALL SECTIONS OF BULLET SURFACES. THE INFORMATION IS QUANTIFIED TO GIVE A LOCAL VERIFICATION SIGNATURE THAT INCLUDES MEASURES OF POSITION, AMPLITUDE, AND WIDTH FOR ALL SIGNIFICANT STRIATIONS IN A SECTION. COMPARISON OF TWO BULLETS IS THEN PERFORMED BY MATCHING ALL CORRESPONDING LOCAL SIGNATURES, LAND WITH LAND AND GROOVE WITH GROOVE, IN SEQUENCE. MATCHES IN STRIATION POSITION, WIDTH, AND AMPLITUDE BETWEEN EACH CORRESPONDING SIGNATURE PAIR ARE REPRESENTED AS PROBABILITIES THAT AT LEAST AS GOOD A MATCH COULD OCCUR AT RANDOM. INDEPENDENCE IS ASSUMED BETWEEN SECTIONS; SO THE TOTAL PROBABILITY OF VERTIFICATION ERROR IS REPRESENTED BY THE PRODUCT OF ALL LOCAL PROBABILITIES. BECAUSE THE STRIATION INFORMATION EXTRACTED IS ESSENTIALLY THAT USED BY BALLISTICS EXPERTS, THE COMPUTER TECHNIQUES CLOSELY PARALLEL STANDARD BALLISTICS PERFORMANCE, BUT ARE ABLE TO PRODUCE AN OBJECTIVE MEASURE OF VERIFICATION. THE LOCAL NATURE OF THE MATCH, FURTHERMORE, ALLOWS VERIFICATION OF DEFORMED AND FRAGMENTED BULLETS. IN ADDITION, USING ONLY THE STRONGER STRIATIONS MINIMIZES THE EFFECTS OF SIGNATURE CHANGES DUE TO GUN BARREL WEAR AND CORROSION. GRAPHS, TABLES, FIGURES, EQUATIONS, PHOTOS, AND REFERENCES ARE PROVIDED (AUTHOR ABSTRACT)