Author ORCID Identifier

https://orcid.org/0009-0006-3073-383X

Semester

Spring

Date of Graduation

2025

Document Type

Thesis

Degree Type

MS

College

Eberly College of Arts and Sciences

Department

Forensic and Investigative Science

Committee Chair

Tatiana Trejos

Committee Co-Chair

Luis Arroyo

Committee Member

Luis Arroyo

Committee Member

Roger Jefferys

Committee Member

Paul Speaker

Abstract

The rise in gun violence in the United States has increased the demand on forensic agencies to process evidence promptly and accurately. The exchange of imperceptible traces among objects, suspects, and victims can provide critical insights into the interactions and sequence of events during a crime. Gunshot residue (GSR) is a type of trace evidence that holds significant investigative value in shooting reconstructions. GSR can help identify potential shooters, intermediate targets, and bullet trajectories; however, its analysis is often expensive and time-consuming. Consequently, there is an urgent need for more effective solutions.

Methods for on-site screening can significantly streamline forensic processes; however, the analysis of GSR poses challenges due to concerns regarding sample integrity. Recently, innovative mobile instrumental techniques, such as Laser-Induced Breakdown Spectroscopy (LIBS) and Electrochemical Devices (EC), have addressed these limitations. For instance, mobile LIBS technology offers advanced capabilities for enhanced imaging, targeted ablation of single particles, sensitive elemental analysis, and mobility to the crime scene. Additionally, EC allows for the simultaneous detection of both inorganic and organic components of GSR. Together, these instruments provide a more comprehensive approach to GSR evidence in a fraction of the time, making them valuable tools for triaging information at crime scenes and forensic laboratories.

Integrating these screening tools into the workflow can expedite informed decision-making processes and reduce costs. This project evaluates the current state of GSR analysis and assesses the readiness of mobile techniques for implementation in laboratories through three main objectives: 1) evaluate current analytical methods and their efficiency in crime laboratories; 2) expand the applicability of mobile LIBS to various trace evidence in firearm-related investigations; and 3) develop an implementation plan for mobile instrumentation in crime laboratories.

Firstly, this study examines the graphical representation and analysis of current GSR workflows in two practicing laboratories, identifying bottlenecks and opportunities for improvement. A survey, distributed by major professional organizations in the field, gathered responses from 56 participants across 19 nations, providing valuable insights into the practical investigative workflows related to GSR evidence, from the initial arrest of a person of interest to the issuance of reports.

The versatility of mobile LIBS extends beyond GSR to encompass a variety of target materials, bullets, and cartridge case residues. Over 400 samples were collected from shooting at eight different substrates—wood, drywall, glass, paint, concrete, and several automotive parts—using three types of bullets: full metal jacket (FMJ), jacketed hollow point (JHP), and lead round nose (LRN). This resulted in either perforation or ricochet. Multi-transfer and cross-transfer of GSR and other traces from impacted substrates and ammunition components were detected via LIBS on the shooter’s hands, bullet holes, and recovered bullets, providing a wealth of data for more rapid and comprehensive analyses.

Finally, a cost-benefit analysis demonstrates that enhanced efficiency is achievable through the adoption of advanced mobile techniques, specifically LIBS and EC methods. Overall, the researcher-practitioner partnerships established in this project provide a solid foundation for technology transfer and illustrate how mobile trace methods can modernize shooting reconstruction investigations, thereby improving both efficiency and accuracy.

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