Law enforcement investigators test the clothing and skin of people for gunshot residue to determine if they were near a gun when it discharged. Gunshot residue can travel over 3–5 feet (0.9–1.5 meters) from the gun. At the farthest distance, only a few trace particles may be present.
How does distance of the muzzle of the gun from the target effect the presence and amount of gunpowder residues?
In theory, the closer a discharged firearm is to an object, the smaller its gunpowder pattern will be; likewise, the more distant, the larger the gunpowder pattern. Many firearms’ gunpowder patterns (or gunpowder particles that impact a target) drop off substantially at approximately 36”-48” .
At what distance is little or no gunshot residue found on the victim?
This confirms the 3-inch minimum distance . The 18-inch standard (right) shows very little lead residue and again confirms the maximum muzzle-to-garment distance. The 12-inch standard (middle) seems a little less concentrated than the lead deposit seen on the evidence shirt.
What is a distance determination how is this done?
An examination of an item of evidence is done to determine if a pattern relevant to distance determination is produced . Once a pattern showing the reaction of nitrite or lead residues is produced, further testing is done in the form of a test fire at different muzzle to target distances.
How is gunshot residue detected?
Gunshot residue (GSR) analysis is a standard method to determine if a firearm has been used. Particles for GSR analysis typically range from 0.5 to 10 microns. Often the primer particles containing lead (Pb) , barium (Ba) and antimony (Sb) are detected and analyzed using EDS in a scanning electron microscope.
What are striation markings left on a bullet called?
Inside the barrels of handguns and rifles are spiral impressions called rifling . The raised portions of the rifling are known as lands and the recessed portions are known as grooves. When a weapon is fired, these lands and grooves cut into the bullet, putting spin on it as it travels through the barrel of a firearm.
Why is gunshot residue examined?
Gunshot Residue and Range of Fire Determination. ... It is usually analyzed forensically for either of two purposes: (1) to determine whether or not a suspected shooter may have fired a firearm, or (2) to estimate the range of fire from muzzle to target .
What removes gunpowder residue from skin?
As time passes after discharge, GSR particles can be removed from the hands by contact with other objects or by hand washing . After 6-8 hours, analysts would not expect to detect GSR on an active person.
Is gunshot residue class or individual evidence?
Examples of trace evidence include paint, explosive debris, glass, dust and dirt, gunshot residue, blood, and other bodily fluids.
What are the types of gunpowder commonly used today?
- Black powder.
- Corned powder.
- Brown powder.
- Smokeless powder.
- Serpentine powder.
- Double-base gunpowder.
- Low explosive.
What tests are commonly used for GSR?
When all three elements were found on a person’s hands, recent exposure to GSR was probable. Since the late 1970’s, the scanning electron microscope (SEM) has been used to identify GSR. This technique is the most reliable laboratory method for GSR identification and analysis.
What is the importance of distance determination?
Distance determination testing is important in cases where the distance a firearm was held from a target or victim becomes crucial in establishing what occurred during the commission of a crime or to establish self-defense (Osterburg & Ward, 2004).
What is bullet wipe?
A “bullet wipe” is a gray or black ring around an entrance bullet hole . The ring is formed by and contains bullet lubricant, byproducts of propellant, traces of bullet metal, and residue in the gun barrel from previous use.
How long does gunshot residue stay on clothes?
component particle is only indicative of the discharge of a firearm, not the discharge of a specific firearm. Are you able to tell how long particles have been present on a surface? an item of clothing containing GSR is left undisturbed for 5 years , the GSR will be the same as the day it was deposited.
Can gunshot residue be washed off clothing?
Yes, it can be washed off . Per Wikipedia, GSR is the consistency of flour and typically only stays on the hands of a living person for 4–6 hours. Wiping the hands on anything, even putting them in and out of pockets can transfer GSR off the hands.
How do they test for GSR?
Gun shot residue is tested by lifting samples off a defendant’s hands or clothing and then testing to see if the lifts contain a fused particle of barium, antimony, and lead, which are known to be present in GSR.
