Using SEM to Accelerate Gunshot Reside Analysis

Thermo Fisher Scientific™ has a physicist and product manager called Jeroen Smulders, who is part of a team which developed the Phenom Perception Gunshot Residue (GSR) Desktop Scanning Electron Microscope (SEM) - the sole desktop SEM which is designed to perform gunshot residue analysis.

The technique is used by Forensic scientists as a means of finding evidence that suspects have discharged firearms. This article outlines GSR’s development history, explaining the details and handling of the Phenom Perception GSR Desktop SEM. It provides examples for situations in which GSR can be utilized.

GSR Analysis

FEI is a microscope company, which has been a subsidiary of Thermo Fisher Scientific since 2016. Smulders began working at FEI as an application manager in 2007, and has been responsible for developing a desktop SEM. Smulders went with the product to Phenom-World (a spin-off company) in 2009, where he worked as an application engineer for seven years.

In this time, he encountered GSR. The company began to develop an SEM designed for GSR analysis on the basis of the Phenom XL. The first GSR conference with the Phenom Perception GSR Desktop SEM got underway in 2015, during the 22nd yearly ENFSI (European Network of Forensic Science Institutes) gathering for Firearms and Gunshot Residues.

ENFSI hosts a yearly gathering of forensic scientists, even delivering a conference specifically for firearms and gunshot residue, in which GSR and ballistic trace experts meet each other. These conferences are convened in order to ensure that people like Smulders are in frequent contact with customers and the market.

Phenom Perception GSR Desktop v Phenom XL

There is an automated scanning routine in the Phenom Perception GSR which makes a significant difference. There are also a number of hardware options which may be picked for the GSR version, such as a motorized z-stage and a bigger EDS-detector.

Difficulties in Development of GSR Analysis in SEM

Developing an SEM which is suitable for GSR application is a different challenge when compared with making one which just produces quality pictures and can perform EDS-analysis on general samples.

This is primarily because of operational stability. Settings such as brightness and contrast must be maintained on a stable level for long periods of time during GSR analysis, as the procedure is liable to last as long as 24 hours in extreme circumstances. Consequently, the Phenom Perception GSR’s accuracy and stability are on the next level when compared to regular SEM.


The beam’s accuracy and stage positioning are also superior. For instance, the routine can detect potential GSR particles during scanning. Following this, it needs to revert in order to perform an EDS analysis.

Clearly, one does not want to analyze spots near to the particle. If one tells the stage to move 100 micrometers to a certain side, it is important to ensure it is definitely 100 and not 110 micrometers. If this is not guaranteed, it is possible to miss an element of the sample and perhaps even GSR particles.

In the event the stage moves less than 100 micrometers,  the same particle may be detected twice. As a result of these possibilities, a high level of instrument accuracy is extremely important.

Forensic scientists and SEM in GSR Particles

GSR analysis using SEM has been going on since the 1980s. It became increasingly automated as computer power improved and electronics became more refined. The results consequently became more reliable.

GSR particles are carried in the cloud of smoke after a gun discharge and deposited on shooters hand and surroundings

GSR particles are carried in the cloud of smoke after a gun discharge and deposited on shooters hand and surroundings

Although, previously the user probably did not have to analyze each image manually. For instance,  Smulders used to work with a pioneer in the field who wrote one of the very first GSR software packages which is no longer in use.

However, this demonstrates that users were already trying to automate the analysis process in the early days. Over time, this has significantly improved and sophisticated routine analysis techniques have been made.

Smulders began in 2013, and in 2014 his company announced the product’s availability. In the intervening years, it has become the sole desktop SEM on the market which is dedicated specifically to GSR analysis.

Customizing the microscope is the very first thing that needs to be done. This means adjusting it to the user’s individual requirements.

Is GSR Analysis Different?

GSR analysis isn’t really any different. Every laboratory follows approximately identical procedures, however the settings’ details vary. This is why defining how the user wants to run the microscope becomes necessary. Although there is a default run, the chances of it matching the user’s exact working method is relatively low.

There are standards for GSR analysis. For instance, these standards may define the particles’ or the scan area’s size range. The guidelines are bespoke, but they still leave a little room for interpretation as certain variables are unable to be defined completely.

Consequently, the method of performing the analysis varies in different labs — particularly when European and American or Asian forensic labs are compared. Each forensic institute has its own method of working in terms of the GSR analysis.


There are many parameters. It is possible to adjust these to the needs of the individual. For instance, it is possible to optimize it for speed or sensitivity, as well as other parameters.

The process may take a number of days or even weeks. However, once the standard operating procedure has been figured out, operating the SEM becomes very straightforward. The user puts in the sample, focuses manually, and then runs the routine.

On the one hand there is a high degree of flexibility, and on the other hand it is extremely simple to use after the standard manner of working has been set.

Discover the First Dedicated Gunshot Residue Solution

Gunshot residue analysis is made on-demand, more quickly, more simply, and more reliably than ever before, courtesy of the Phenom Perception GSR.

As many as 30 samples can be put in simultaneously and there is even room for some calibration samples.

This is more than enough for the majority of customers. Generally, less than this amount is analyzed at the same time. For example, the majority of laboratories will not mix samples from different suspects.

If we assume there are six different suspects, six separate runs are performed — generally with between three and five samples for each. This is intended to avoid cross-contamination or to straightforwardly prevent the samples being mixed up.

The sample holder which is used most widely is a sticky disc which has a diameter of 12 millimeters. It is possible to analyze this entire area.

Anywhere between 0 and 1,000 particles, or even in excess of 10,000 particles, can be found on a GSR sample. It depends largely on the circumstances, such as which gun has been used, which ammunition, and which location (whether outdoors or indoors).

Investigators do not generally still collect samples from crime scenes to see whether a firearm was used as there are often significantly more obvious traces, such as cartridge cases on the floor or a hole in the wall. As such, GSR is applied only when there is already evidence a firearm was used, rather than the other way around.

While suspects are the main source of samples, it is still common practice to take samples from victims. This can, for example, tell investigators if the victim has used a firearm as well.

In instances of potential suicide, it is possible to gather evidence of whether or not the victim has used the firearm in order to take their own life. Significantly more GSR particles will be present on the victim as compared to cases where another individual has fired the gun.

It is difficult to determine the number of particles required for a positive outcome. Clearly, zero particles constitutes a negative result. However, this still does not necessarily mean no gunshot was fired. There are discussions as to whether one GSR particle constitutes a positive result. It depends entirely on who is asked. Some, for instance, say that at least three GSR particles are required.

It is hard to determine exactly what a positive GSR outcome means as it is generally accepted that GSR particles do not only come from firearms. They may, for instance, be picked up via secondary processes. Shaking the hand of a person who has shot a firearm recently may deposit GSR particles on your hand.

The presence of GSR alone is not sufficient – it is always presented as supplementary evidence. For instance, if investigators locate GSR-particles on a person’s hand and that person’s neighbor was killed the previous night, this does not guarantee that the person in question murdered their neighbor. It is only one aspect of a complex jigsaw. This aspect gains weight if investigators locate several GSR particles on a sample and loses validity if they locate just a few.

GSR analyses performed with a Thermo Scientific Phenom Perception GSR Desktop SEM

GSR analyses performed with a Thermo Scientific Phenom Perception GSR Desktop SEM

Analyses are not really faster if there is no particle on the sample. All particles on the sample must be scanned in order to ensure that they are all negative. Generally, there are a number of environmental particles on any given sample — normally between 1,000 and 5,000. It takes time to scan each one.

The particle’s chemical composition is determined via an energy dispersive spectroscopy (EDS)-analysis. Using this method, it is possible to distinguish GSR particles from other types of particle.

GSR particles have a unique chemical composition. Once the scanning process is complete, a report informs the user the number of GSR particles that were detected. At this point, the user must verify and confirm that each of these positive particles are actually GSR particles. In order to do so, a forensic analyst is able to produce a high-magnification image for morphology reasons, as well as performing a manual EDS analysis to produce a high-quality EDS-spectrum.

In the majority of cases the software does not have a high error rate. The software is designed in such a way to make sure that the user has to reject positive particles as little as possible. Overall, the product has a low error rate.

The customers’ feedback has been positive. There are strong reasons why customers appreciate this product a great deal. Normal forensic laboratories have large electron microscopes and all types of forensic analysis are performed with these instruments.

GSR analysis is not the only use of SEM. If a user runs GSR, the SEM is taken up for numerous hours and sometimes longer. In this context, it makes sense for several forensic laboratories to have an additional SEM which is dedicated solely to GSR analysis. The Phenom Perception GSR does not take up a great deal of space as it is a small desktop SEM and it is also relatively simple to use.

Thermo Scientific Phenom Perception GSR Desktop SEM

Thermo Scientific Phenom Perception GSR Desktop SEM

A scanning electron microscope (SEM) can be used during GSR tests in order to scan the sample and identify suspect GSR particles. In order to verify whether gunshot residue elements such as barium (Ba), Antimony (Sb), and lead (Pb) are present in the sample, the Energy Dispersive Spectroscopy (EDS) technique is used.

As the system is automated, users can speed up the process of forensic.  Gun-shot residue analysis is made on-demand, more quickly, more easily, and more reliably than ever before thanks to the Phenom Perception GSR. It is ideal for every busy GSR forensics lab that needs to save floor space and time.

This information has been sourced, reviewed and adapted from materials provided by Thermo Fisher Scientific Phenom-World BV.

For more information on this source, please visit Thermo Fisher Scientific Phenom-World BV.


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