Using shattered glass to gather clues from crime scenes is a well-established practice, but a new approach may take this to another level. Assistant Professor Shirly Montero of Arizona State University’s School of Interdisciplinary Forensics is studying how microscopic glass particles embedded in bullets can be used as evidence in criminal investigations.

Montero’s research focuses on analyzing glass particles smaller than half the width of a strand of hair, which are often found embedded between the lead slug and copper jacket of a bullet. This new method aims to help forensic experts distinguish between different pieces of glass when multiple crime scene scenarios are possible. Known as “comparative analysis,” it involves comparing the chemical composition of one piece of glass to another to rule out certain scenarios.

Montero, who has studied glass for more than 25 years, was inspired to research glass on bullets after a forensic firearms examiner approached her regarding a police-related shooting involving a vehicle. Her analysis could help determine whether a bullet was fired through the windshield in self-defense or through a passenger window, which might suggest an unjustified shooting.

Montero’s expertise as a glass analyst and her experience as a volunteer crime scene specialist have positioned her to push the boundaries of this forensic technique. However, using microscopic glass fragments embedded in bullets is not yet common practice in crime-solving. “We are one of the few labs that have the capability of doing this,” Montero said, noting the need for multiple studies to validate the method and establish its value for courtroom use.

To advance this research, Montero is utilizing a laser ablation instrument and an ICP-MS (inductively coupled plasma mass spectrometer) at ASU’s Metals, Environmental and Terrestrial Analytical Laboratory. The laser extracts a subsample of the glass powder, which is then analyzed to measure 17 chemical elements, creating a chemical profile that can be compared to possible sources of glass involved in a bullet’s trajectory. Montero aims to ensure this process can withstand the scrutiny of legal proceedings.

To streamline the analysis, Montero is partnering with a software developer from Serva Energy to automate the signal processing step. She has already presented her work at the American Academy of Forensic Sciences and the Association of Firearm and Toolmark Examiners, with plans to make her findings available to experts by the end of the year.

Montero hopes that analyzing glass from bullets will eventually become a regular tool for detectives. “Many times, forensic examiners are not making use of all of the valuable material at a crime scene,” she said. “My hope is to bring awareness of the technique of analyzing glass from bullets and support them in whatever scenario I can.”

Republished courtesy of ASU

Original authors: Dolores Tropiano (Reporter, ASU News)

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