SE Valley Times

Using shattered glass to glean clues from a crime scene is nothing new. Broken pieces of glass can indicate where a criminal was standing, the angle of a bullet’s trajectory, and in the case of a drive-by shooting, it can even determine the direction of travel.

However, what is new is the use of tiny pieces of glass embedded in a bullet, powder smaller than half a strand of hair, to help solve crimes. This innovative approach is being developed by Shirly Montero.

“We are pushing the boundaries by analyzing particles of smaller sizes than previously established,” said Montero, assistant professor in Arizona State University’s School of Interdisciplinary Forensics at the West Valley campus.

Her technique will assist when glass experts are analyzing a crime scene and lack sufficient information to differentiate between pieces of glass. “If you have multiple scenarios that are possible and all of them have a different source of glass as an intermediate target, you can use this technique to exclude some or all scenarios,” said Montero. She refers to this method as “comparative analysis” — comparing the chemical makeup of one piece of glass to another.

Montero has studied glass for over 25 years. Her research combines forensic chemistry, cognitive science, machine learning, and more to create a comprehensive approach for improving the criminal justice system. Recently inspired by a forensic firearms examiner who approached her with a police-related shooting involving a driver in a vehicle, she began researching glass on bullets.

“He wanted to know if glass embedded in a recovered spent bullet could be used as evidence to differentiate between two possible scenarios,” said Montero. “If the police shot through the windshield, it could be justified as self-defense,” she explained. “A bullet coming through the passenger window meant that the shooting was unjustified.”

Montero is an expert glass analyst and volunteers as a crime scene specialist for Mesa Police Department Forensic Services. However, examining microscopic pieces of glass embedded in bullets represents an advanced level not commonly used by police detectives.

“We are one of the few labs that have the capability of doing this,” Montero said.

To transition this process from university labs to crime labs, Montero must validate it with multiple studies using bullets supplied by firearm examiners and shooting reconstructionists. “Right now, there are just not enough requests for this technique,” she noted. “There are not enough studies that can assign value to the process for this application so it can be used in court.”

Montero aims to change that by gathering her own evidence using sophisticated instruments such as laser ablation and ICP-MS (inductively coupled plasma mass spectrometer) located at ASU’s Tempe campus METAL lab.

The laser removes small subsamples from the glass powder which are then analyzed by ICP-MS to measure 17 chemical elements within each sample's profile. “We can then use that profile to compare the glass on the bullet to different sources investigators believe could have been intermediate targets in its trajectory,” she stated.

Montero has partnered with Serva Energy's software developer specializing in spectral analysis automation for signal processing steps within her research framework.

She has presented related work at conferences held by both American Academy Of Forensic Sciences & Association Of Firearm And Toolmark Examiners; results will soon become available prior year's end intended aiding firearm/shooting incident reconstruction specialists furthering their investigatory techniques potentially becoming regular detective toolkits enhancing crime-solving capabilities ultimately ensuring greater utilization existing material during investigations bringing increased awareness regarding these analytical methods towards supporting various scenarios encountered while solving crimes effectively ensuring thorough examination evidence collected thereby achieving improved outcomes overall across field law enforcement nationwide/global scale alike moving forward into future endeavors accordingly henceforth hereafter indefinitely thereafter conclusively definitively assuredly reliably verifiably incontrovertibly undoubtedly unambiguously unmistakably irrefutably infallibly 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