Author ORCID Identifier

https://orcid.org/0009-0009-5976-1692

Semester

Summer

Date of Graduation

2026

Document Type

Thesis

Degree Type

MS

College

Eberly College of Arts and Sciences

Department

Forensic and Investigative Science

Abstract

Criminal outbreaks and gun violence persist as a multifaceted global crisis, marked by escalating rates of homicide, suicide, and terrorism that destabilize communities and strain public resources. The proliferation of illicit firearms and homemade explosive devices, along with the complexity of modern criminal networks, necessitates innovative scientific tools to strengthen preventive intelligence operations and ensure that the legal process is grounded in physical evidence. More efficient detection of traces left behind at a crime scene can help prevent further harm or injury from follow-up attacks. This study aims to develop and evaluate new triage methods for characterizing gunshot residues (GSR) and materials used in the fabrication of improvised explosive devices (IEDs), specifically electrical tapes, including laser-based spectroscopy and chromatography coupled to mass spectrometry and electrochemical detection.

The first objective of this project is to detect and characterize electrical tape and black powder using a novel Laser-induced breakdown spectroscopy (LIBS) method designed for on-scene deployment. Improvised explosive devices are often homemade devices using easily available materials. They consist of an initiator, a switch, the main explosive charge, a power source, and other materials added to increase lethality. Among the most common main charges in IEDs is black powder due to its easy accessibility, while electrical tape is often used for wiring, insulation, and securing components to the device. An electrical tape dataset containing samples of known origin (tape rolls of various brands, quality grades, and countries of manufacture, as well as tape sampled from the same roll or package) is used to assess the method's ability to discriminate between tapes from different sources and to classify and associate tape fragments with the source roll. The dataset consists of 21 tapes: a) 15 of which represent different tape sources with 45 fragments (3 fragments per tape, 3 replicates per fragment), b) 10 sections from the same roll to assess intra-roll variations (3 fragments per section, 3 replicates per fragment),  and c) a subset of 10 samples from an interlaboratory study that includes same-source, same-package, and different source tapes to estimate error rates across methods and examiners. The mobile LIBS performance is comparable to other elemental methods, such as benchtop LIBS and micro-X-ray fluorescence (µXRF), yielding false inclusions and false exclusions of under 2%, depending on the comparison criteria.  To create black powder residues, samples are collected on the adhesive layer of the electrical tape (n=10) and on the shooter's hands (n=10) using a muzzle-loading rifle to simulate the detonation in an explosion. Additionally, particles are placed on the adhesive and ignited to simulate partially burnt residues (n=6) and compared with the composition of the neat undetonated powder. The study shows that mobile LIBS is an effective technique for characterizing electrical

tape and explosives, highlighting the method's feasibility for linking samples or scenes within a few minutes and generating rapid on-site investigative leads in explosive investigations.

As a second objective, this study assesses storage and analytical methods that can facilitate the adoption of organic gunshot residue (OGSR) examinations in forensic agencies. The analytical approach employs Gas chromatography-mass spectrometry (GC-MS) equipped with complementary detectors: a flame ionization detector (FID) and a micro-electron capture detector (µECD). The study compares this method to three other previously validated methods using a shooter (n=20) and non-shooter dataset (n=20), including GC-MS, gas chromatography-tandem mass spectrometry (GC-MS/MS), and liquid chromatography-tandem mass spectrometry (LC-MS/MS). The findings indicate that GC-MS/µECD is a cost-effective method with performance comparable to LC-MS/MS, offering competitive detection limits (1 – 90 ppb) and overall accuracy (>90 %). Meanwhile, the FID detector is unsuitable for trace-level OGSR analysis due to its higher limits of detection (30–110 ppb) and lack of selectivity. The study also evaluates the suitability of samples exposed to a high-heat storage environment to simulate situations in which they cannot be submitted to the laboratory immediately. The dataset includes 70 samples, split between storage inside a vehicle and freezer storage, over five intervals (t=immediate, 2 days, 1 week, 2 weeks, 1 month) to determine how OGSR concentrations are affected with time since collection and temperature conditions. The results show that OGSR remains stable even at temperatures as high as 39 ºC, due to the sealed storage stub and the presence of OGSR microparticles alongside vapor-deposited traces.

This project offers several recommendations for rapid on-site methods for inorganic GSR, tape, and explosive analysis, as well as for storage and analytical workflows for OGSR. These advancements can transform current workflows in firearm and explosive investigations by achieving high-tier analytical results, even in resource-constrained environments.

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