Forensics lab cracks case on newer, 'greener' gunshot residue

Date:
July 6, 2023
Source:
West Virginia University
Summary:
Discoveries by forensic scientists about how gunshot residue behaves
on skin, hair and fabric will allow crime scene investigators
to catch up to the proliferation of new, eco-friendly types of
ammunition and make faster, more informed decisions at crime scenes
and in forensic laboratories.


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FULL STORY ========================================================================== Discoveries by West Virginia University forensic scientists about how
gunshot residue behaves on skin, hair and fabric will allow crime scene investigators to catch up to the proliferation of new, eco-friendly
types of ammunition and make faster, more informed decisions at crime
scenes and in forensic laboratories.

Lead and other toxic components of ammunition are crucial in establishing
the presence of gunshot residue, or GSR, at crime scenes. However,
heavy metals like lead aren't present in new "green" ammunitions that
are changing the rules for GSR analysis, according to Tatiana Trejos,
associate professor in the Eberly College of Arts and Sciences Department
of Forensic and Investigative Science.

"A major forensics discovery was that, when you fire a gun, a cloud of particles is produced by the primer, the material that explodes and causes
a bullet to eject. The primer contains, among other things, inorganic compounds, heavy metals like lead, barium, antimony," Trejos said.

"When this cloud touches our skin, tiny particles remain there. The
composition of those particles is specific to firearm discharge -- we
don't commonly find that combination of metals in other conditions. That realization was a big help to forensic scientists in firearms-related investigations." But over the years, ammunition has changed. More primers
are manufactured without metals harmful to the environment and human
health. That's a challenge for GSR analysis and the reason forensic
science -- a field that uses scientific methods to help solve crimes
and examine trial evidence -- is looking beyond inorganic compounds like
metals to organic compounds like nitroglycerine that are also released
when a gun fires.

"If we combine information about organic and inorganic compounds in GSR,
we can have more confidence in our results," Luis Arroyo, an analytical
chemist and associate professor, said. "For over a decade, scientific
groups have said we need to know more about organic gunshot residue. We're missing opportunities to confirm the presence of GSR, and this research
funded by the National Institute of Justice is helping to narrow that
gap." The research establishes how organic and inorganic compounds in
GSR differ in the ways they each persist on surfaces and transfer to
other surfaces during activities like running, hand shaking or washing.

Trejos and Arroyo published the results of the studies in a Forensic
Chemistry paper co-authored with WVU graduate students Courtney Vander
Pyl, Kourtney Dalzell, Korina Menking-Hoggatt and Thomas Ledergerber.

To gather data, the team created new and improved organic and inorganic
GSR "reference standards" or methodologies for creating standardized
mixes of particles that accurately mirror real-world gunshot residue,
allowing different labs to meaningfully compare results.

They applied those particles to fabrics, to the skin and hair of real
human volunteers and to an artificial skin product called Strat-M. Then
they subjected those surfaces to real and simulated activities like
running, struggling, washing and rubbing, before measuring the remaining particles.

Trejos said the experiments established Strat-M as a viable substitute
for human skin.

"Artificial skin has been used by fields like pharmaceuticals, cosmetics, health sciences. Now we have proved it can provide a consistent forensic standard while allowing us to test conditions that wouldn't be feasible or
safe for a person's skin." The researchers found inorganic GSR particles persist longer on a surface -- a palm, a sweatshirt -- than organic
compounds, but they're more susceptible to being lost or transferred
by common activities. A shooter who washes their hands with soap and
water, then dries them with a paper towel, will likely prevent crime
scene investigators from identifying GSR based on analysis of lead,
barium and antimony particles on their hands.

The fact that inorganic particles persist over time and are significantly
lost only due to outside forces can be critical to questions about
whether someone is the victim of a suicide or homicide, Trejos said.

Organic compounds, conversely, may be lost from clothing if a suspect
struggles during arrest, but they are less likely to transfer to someone
else, like the arresting officer.

Up to 100 characteristic inorganic particles could transfer from one
person to another during a handshake, compared to no transfer at all
for organic compounds. But unlike inorganic particles, organic particles
are lost over time due to factors like evaporation from the skin.

Trejos said the next step is to put the findings to use in combination
with another methodology the group recently developed, which allows
field CSIs to immediately analyze possible GSR at a crime scene.

As enthusiastic as Trejos is about the research, she emphasizes that
real-life CSIs don't have as many answers as the ones on television.

"Right now, we can do a pretty good job answering the question, 'Is
GSR present or not?' But the next and more interesting question is,
'Did this person fire the gun?' Forensics is not always able to answer
that with high certainty. This research opens new avenues to answer
questions relevant to a judge or jury.

"By providing faster and more informative investigative tools, we're
helping to apprehend offenders with more solid evidence, and we're
minimizing the potential for false incarcerations."
* RELATED_TOPICS
o Health_&_Medicine
# Forensics # Skin_Care # Cosmetics
o Matter_&_Energy
# Forensic_Research # Chemistry # Organic_Chemistry
o Science_&_Society
# Justice # Legal_Issues # STEM_Education
* RELATED_TERMS
o Forensics o Hair o Forensic_toxicology o Identity_theft o
Prison o Acne o Hair_follicle o Parachute

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========================================================================== Journal Reference:
1. Courtney Vander Pyl, Kourtney Dalzell, Korina Menking-Hoggatt,
Thomas
Ledergerber, Luis Arroyo, Tatiana Trejos. Transfer and persistence
studies of inorganic and organic gunshot residues using synthetic
skin membranes. Forensic Chemistry, 2023; 34: 100498 DOI: 10.1016/
j.forc.2023.100498 ==========================================================================

Link to news story: https://www.sciencedaily.com/releases/2023/07/230706152735.htm

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