Gunshot Residue Expert Witness
Gunshot residue (GSR) is a forensic science test on the hands and clothing of an individual to identify whether that person has discharged a firearm. Although, the dermal nitrate test is obsolete, science and technology are constantly developing more reliable tests, such as “The Scanning Electron Microscopes” (SEM.) This devise allows the examiner to see the microscopic samples accumulated, as well as the analysis of the particles present.
Gunshot Particles Fly Onto Skin & Clothing of Shooter
Dermal Nitrate Test
Gunshot residue contains particles that when a gun is fired those particles fly onto the skin and clothing of the shooter, and their immediate, surrounding area. For decades the dermal nitrate test had consisted of collecting these particles by applying melted paraffin wax to the suspect’s hands in order to detect the presence of nitrates. However, this test is no longer valid to determine that a particular person has fired a gun because the courts have observed that in the United States the presence of nitrates in the environment is a common event.
Lateral Angle Determination For Bullet Holes In Windshields
Long-Lasting Effect
Since many people in the U.S. shoot guns, things surrounding them are covered with GSR. Hence, it is important to notice that GSR can land on anything with long-lasting effect. In other scenarios, individuals may also be contaminated with GSR if they were in contact with the shooter or any thing they touched. If tested for GSR, those individuals may test positive. Therefore, if examiners find GSR, it can come from anywhere. Prosecutor’s view is that if someone have not left the firing area; then, that person discharged the firearm. This argument is irrelevant in countries like the U.S. where the presence of particles in the surroundings is a common occurrence. On the other hand, this argument may hold a great weight in countries where guns are uncommon.
Probative Evidence
Additionally, in criminal investigations, even the smallest piece of evidence, or lack of evidence, can help to find out what actually occurred. Although, GSR can be critical, probative evidence, in a criminal case, it cannot assure and point to one person, as DNA can. However, it can determine whether or not a GSR collection is present on a person or an object. Once a GSR collection is found, a gunshot residue expert witness can establish how it landed based on one of three ways :
- a person discharged a firearm;
- the person or thing was in close proximity to a discharged firearm; or
- the person touched an object that had GSR on it.
Laboratory Test Validation In Causation Analysis
Absence of GSR
Even though, GSR evidence is crucial to an investigation since it implies that an individual has been exposed to a GSR particles, the absence of GSR does not mean that the particular individual have not discharged a firearm, for the following reasons; the time has elapsed, activity, weather, washing hands, clothing, or surfaces, concealing from biological material, firearm or ammunition were not good depositors.
Important to Hire Gunshot Residue Expert Witness
Therefore, it is important to hire a gunshot residue expert witness for your case since it would help the jury to determine if the suspect has discharged the gun because the prosecutor in most cases wants only to see what it takes to resolve the crime.
