#37 BANG BANG: GSR Analysis

Aiza Jamil
Dec 24, 2025
3 min read

Hello, and welcome back, folks, to another episode of STEM on the Streets! If you are new here, my name is Aiza, and this is my partner, CAI (crime AI). Together, we stroll through the criminal-ridden streets of STEM!

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Understanding Gunshot Residue Analysis

Gunshot residue analysis (GSR) is one of the most important tools in forensic ballistics. Using GSR, investigators determine whether a suspect was near or involved in a firearm discharge, supporting other evidence in criminal investigations. Today, folks, we dive into the world of gunshot residue analysis.

What Is Gunshot Residue?

Gunshot residue is made of microscopic particles produced when a firearm is discharged. These particles come from a combination of partially or completely burned primer and propellant material, as well as tiny fragments of metal from bullets and cartridge cases. GSR can deposit on hands, clothes, hair, and any surfaces close to the shooter. The most characteristic elements in inorganic GSR are lead (Pb), barium (Ba), and antimony (Sb), which are commonly found in primer compounds.

Although GSR evidence is very useful and strong in many respects, it cannot be interpreted in isolation, as it primarily complements other types of forensic evidence.

Why GSR Matters in Forensics

GSR is important because it can help forensic experts and investigators identify if the suspect was near the firearm discharge, support other pieces of forensic evidence and testimonies, and reconstruct the crime scene or events of the shooting.

Once again, GSR alone cannot conclusively prove that a person fired the gun, as it can be transferred secondhand or removed by washing, rubbing, or other environmental factors.

Collecting GSR: Timing and Technique

Having the GSR collected and sampled properly is critical. There are many different sampling methods, such as adhesive tapes, which can be applied to hands, face, hair, or clothing to lift residue. There are also sticky carbon tapes on stubs, which are often used for SEM analysis (we’ll get to that in a moment) to secure and transport samples.

Timing is key as GSR particles can disappear quickly, so samples need to be collected as soon as possible after a shooting.

The Gold Standard in GSR Analysis

There are many different methods to analyze GSR, but the golden standard is SEM-EDX, Scanning Electron Microscopy (combined with) Energy Dispersive X-ray Spectroscopy. It is a rather big and fearful name, but don’t worry, we’ll simplify it for you. CAI!

(✿◡‿◡)CAI: Yes?

Would you care to do the honours, please?

(✿◡‿◡)CAI: Don’t mind if I do.

SEM scans samples using an electron beam to create high resolution imahes of microscopic particles. Then EDX, also known as EDS, measures the elemental composition of each particle, which confirms the presence of key primer elements. It is used with the SEM as the electron beam that causes the atoms of the element to emit a characteristic X-ray, which can be used to identify specific elements.

Together, both these techniques proved a visual confirmation and chemical identification, making it a standardised method in forensic laboratories.

Interpreting GSR Results

Ok, so this is where the fun comes in, the actual analysis. Once the results must be interpreted carefully. Due to the fact that each element has its own characteristic X-ray, by analysing the X-ray spectrum which is emitted, the chemical composition of particles can be identified. This means it can confirm whether GSR was there by checking for specific X-ray emission for lead, barium, and antimony.

Well, that is all for today, lovely people! Next blog, we’ll be diving further into the world of forensic ballistics

This is Aiza Jamil signing out!

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