Forensic Analysis Weighing Bullet Lead Evidence

Reduction

The chemical process of converting the lead ore into molten lead

Refining

The process of removing unwanted contaminants by various treatments carried out on a bath of molten lead

REM

Remington, bullet manufacturer

Radio-Frequency

RSD

Relative Standard Deviation

Antimony, an element used to harden lead for bullets.

Standard Deviation

Secondary lead smelter

An organization that remelts scrap lead from various sources and carries out refining and alloying operations to produce lead ingots, pigs, billets, etc. of specified composition for further processing and/or product formation

Slug

A cylinder of lead that has been cut for an extruded wire and that approximates the size (length and diameter) of the finished bullet

Tin, a metallic element also used for hardening lead, but it is more expensive and less effective than antimony. Also a metal sometimes present as an impurity in bullet lead

SRM

Standard Reference Material

SSMS

Spark Source Mass Spectrometry

Suspect bullet

Unused cartridges in the possession of a suspect

Swage

An operation that involves rotary forging, employing rotating dies that periodically open and close, used to reduce the diameter of rods, wires, or tubes. (Often used in the firearms industry to mean pressing of a slug into a bullet.)

TIMS

Thermal Ionization Mass Spectrometry

WDXRF

Wavelength Dispersive X-Ray Fluorescence

WIN

Winchester, bullet manufacturer

Wire

A long piece of lead of the correct diameter used to produce a desired caliber bullet, formed by extrusion

Statistical Terminology

K_a

critical value

t_a

critical value

within-bullet standard deviation

Table of Contents

Front Matter R1-R12

Executive Summary 1-7

1. Introduction 8-11

2. Compositional Analysis 12-25

3. Statistical Analysis of Bullet Lead Data 26-70

4. Interpretation 71-108

5. Major Findings and Recommendations 109-114

Appendix A: Statement of Task 115-117

Appendix B: Committee Membership 118-123

Appendix C: Committee Meeting Agendas 124-129

Appendix D: Glossary 130-132

Appendix E: Basic Principles of Statistics 133-141

Appendix F: Simulating False Match Probabilities Based on Normal Theory 142-150

Appendix G: Data Analysis of Table 1, Randich et al. 151-156

Appendix H: Principal Components Analysis: How Many Elements Should Be Measured? 157-162

Appendix I: The Birthday Problem Analogy 163-164

Appendix J: Understanding the Significance of the Results of Trace Elemental Analysis of Bullet Lead 165-168

Appendix K: Statistical Analysis of Bullet Lead Data by Karen Kafadar and Clifford Spiegelman 169-214

Statistical Terminology