Analysis of gunshot residues helps in determining the various components present, such as barium
Barium
Barium is a chemical element with the symbol Ba and atomic number 56. It is the fifth element in group 2 and is a soft, silvery alkaline earth metal. Because of its high chemical reactivity, barium is never found in nature as a free element. Its hydroxide, known in pre-modern times as baryta, …
Antimony
Antimony is a chemical element with the symbol Sb and atomic number 51. A lustrous gray metalloid, it is found in nature mainly as the sulfide mineral stibnite. Antimony compounds have been known since ancient times and were powdered for use as medicine and cosmetics, often known by …
Nitrate
Nitrate is a polyatomic ion with the molecular formula NO⁻₃ and a molecular mass of 62.0049 u. Organic compounds that contain the nitrate ester as a functional group are also called nitrates.
Full Answer
Why is gunshot residue important evidence?
Gunshot residue is increasingly used as forensic evidence in cases where guns have been used to commit a crime. Gunshot residue materializes whenever a firearm is discharged. When the trigger is pulled, fire is sent into the cartridge the intense heat burns the gunpowder and converts it into gas.
Can gunshot residue be washed off or wiped off?
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. Accordingly, does washing your hands get rid of gunshot residue?
What is the best way to remove gunpowder residue?
- Remember not to eat or drink till you’ve cleaned up.
- Depending on how far you want to take it:
- Wash your hands and face in cool/cold water and soap first. ...
- You may want to wash your clothes as they will be contaminated.
- Take a shower.
- You may want to think about keeping a specific hat, pair of gloves, or shoes for just when you shoot.
Do silencer guns leave gunshot residue?
Neither implication holds up to the facts. A gun “silencer” or suppressor operates by “containing” the gases and fiery exhaust that are released upon the firing of a bullet. This release of high pressure gas and exhaust results in the loud sound associated with gunshots.
What does a positive gunshot residue mean?
Mainly it indicates that the person sampled was either in the vicinity of a gun when it was fired, handled a gun after it was fired, or touched something that was around the gun when it was fired. (For example: When a person goes to the aid of a victim of a gunshot wound, some gunshot residue particles can transfer from the victim.)
What are the elements that are found in gunshot residue?
Lead, antimony, and barium. Barium, calcium, and silicon. Antimony. Barium. The authors proposed some rules about chemical elements that could also be present in these particles. Wallace and McQuillan published a new classification of the gunshot residue particles in 1984.
How long does gunshot residue stay on your hands?
Gunshot residue 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 gunshot residue off the hands.
How far can you see gunshot residue?
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.
What was used to take a cast of a suspect's hand?
Before the use of the scanning electron microscope hot paraffin wax was used to take a cast of the suspect’s hand. The cast was then sprayed with a reagent giving a coloration with nitro-compounds from the partially burnt and unburnt propellant particles. This approach, introduced in 1933 by Teodoro Gonzalez of the Mexico City Police Laboratory, ...
What is a GSR?
Gunshot residue (GSR), also known as cartridge discharge residue (CDR), "gunfire residue" (GFR), or firearm discharge residue (FDR), is residue deposited on the hands and clothes of someone who discharges a firearm. It is principally composed of burnt and unburnt particles from the explosive primer, the propellant —and possibly fragments ...
What is the purpose of gunshot residue analysis?
Analysis of gunshot residues helps in determining the various components present, such as barium, antimony, nitrate, and lead that plays a vital role in determining the primers and propellants used in the weapon, which in turn helps in the identification of weapon used, the range of firing and also identify the shooter.
What is the effect of gunshot residue on neutron activation?
The examination of gunshot residue by neutron activation analysis detects the presence of antimony and barium. When the gunshot residues are exposed to neutron bombardment in a nuclear reactor, antimony and barium capture one neutron to give radioactive antimony and radioactive barium.
What is GSR in firearms?
FORENSIC ANALYSIS OF GUNSHOT RESIDUE (GSR) Gunshot residues are produced when a cartridge is fired from a firearm. They are also known as firearm discharge residue or powder residues. Gunshot Residue is usually found on hands, clothes, target, on the articles found around the targets, and is also found floating in the air.
What does it mean when a gun is discharged from a close range?
1. Visual examination. In cases where the firearm is discharged from a close range, the visual examination may reveal burning, blackening, tattooing, etc. Their presence indicates a gunshot injury or a gunshot hole. 2. Infrared photography. If bullet holes are on colored clothes, the presence of gunshot residue is masked.
What is the best way to see bullet holes in clothes?
2. Infrared photography. If bullet holes are on colored clothes, the presence of gunshot residue is masked. Infrared photography proves helpful in such cases, and the gunshot residue becomes visible in photographs. 3.
How does an element absorb radiation?
An element absorbs the radiation of the same wavelength as it emits when excited. The suspected element is taken into an atomizer and is excited by heating. The radiation from a discharge tube with the suspected metal electrodes is passed through the atomizer.
What is the color of nitrates on a paraffin wax cast?
The picked-up residues on the cast are treated with diphenylamine dissolved in strong sulphuric acid. The appearance of blue color spots indicates nitrates which in turn are indicative of gunshot residues.
What happens if a defendant refuses to test for GSR?
At least one state Supreme Court case has specifically held that if a defendant refuses to consent to a GSR test, the fact of that refusal is admissible at trial as evidence of guilt. See State v. Odom, 303 N.C. 163 (1981) (evidence of defendant’s refusal was properly admitted at trial: “In conclusion, we hold that the admission of testimony concerning defendant's refusal to submit to the gunshot residue test did not violate her constitutional right to counsel and did not deprive her of due process of law.”).
What happens when you pull the trigger on a gun?
In short, when a person pulls the trigger on a gun, this causes the firing pin to strike a “primer” located at the base of the cartridge. That primer strike, in turn, sparks a chemical reaction inside the cartridge that ignites the gunpowder, and the resulting explosion propels the bullet out of the barrel of the gun.
What is a GSR test?
A gunshot residue (“GSR”) wipe test detects the presence of distinctive chemicals that are deposited on a person’s skin or clothing or other nearby surfaces when a gun is fired. GSR tests results are considered reliable, and should be admitted into evidence. Gunshot residue can be removed by actions such as washing hands, wiping clothing, ...
Is a gunshot residue test a non-intrusive test?
See State v. Coplen, 138 N.C. App. 48 (2000) (like other procedures described in G.S. 15A-271, “a gunshot residue test is a relatively non-intrusive procedure” and it “falls within the broad language [of] ‘similar identification procedures’ in that it is comparable to handwriting exemplars, voice samples, photographs, and lineups”).#N#However, because a gunshot residue wipe must be taken within a few hours of the shooting to have any value, and because the residue can be easily removed or destroyed by normal activities such as hand-washing or reaching into a pocket, appellate courts have upheld the admissibility of GSR tests done in the absence of a court order based on a showing of exigent circumstances and probable cause. See, e.g., State v. Page, 169 N.C. App. 127 (2005) ; State v. Coplen, 138 N.C. App. 48 (2000) .
What happens when a gun is discharged?
When the firearm is discharged, these particles are ejected from the cylinder gaps, ejector ports, and the end of the barrel, resulting in a plume of residue in the air around the gun. This residue can land on nearby surfaces and objects, including the hands of the shooter. To determine if GSR could be present, ...
Why is a gun test negative?
Therefore, someone who fired a gun may test negative because a detectable amount of GSR was not deposited. Time lapse between the shooting of a weapon and the collection of the kit may also lead to negative GSR results.
What is GSR in firearms?
The lab may be able to assist with such investigations through the use of gunshot residue (GSR) analysis. GSR is typically expelled from a firearm upon discharge and can land on individuals in close range of the firearm. GSR kits are designed to collect these particles, and the Trace evidence section of the lab has the equipment and expertise to analyze these kits. While GSR testing can provide important information for your case, there are limitations in what the results indicate in a shooting incident.
How long does it take for GSR to be detected?
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.
How long does it take for a steering wheel to test positive for GSR?
All three steering wheels tested positive for GSR, even when the sampling was conducted 1-4 days after the examiners had last discharged a firearm. GSR generated from a firearm discharge can be deposited onto objects in close range, which include the firearm itself.
What can GSR tell investigators?
There are limitations in what GSR results can tell investigators who are reconstructing a shooting incident. However, GSR analysis still has a place in the investigation as a useful tool in putting the pieces of the puzzle together, especially when GSR results are interpreted in conjunction with other evidence. The science of GSR detection is sound, and the lab can confidently report the presence or absence of GSR. The real challenge is in the interpretation of how the GSR was deposited.
What is a negative GSR?
Negative GSR Kits. A common misconception is that a negative GSR result is proof that a person did not actually fire a weapon. There are several mechanisms as to why someone who fired a gun could test negative for GSR. GSR analysis instruments have a detection limit.
Overview
Current practice
In the latest ASTM Standard Guide for GSR analysis by Scanning Electron Microscopy/Energy Dispersive X-ray spectrometry (SEM-EDX) particles containing lead, antimony and barium, and respecting some rules related to the morphology and to the presence of other elements are considered characteristic of GSR. The most definitive method to determine whether a particle is characteristic of or consistent with GSR is by its elemental profile. An approach to the identificat…
History
Before the use of the scanning electron microscope hot paraffin wax was used to take a cast of the suspect’s hand. The cast was then sprayed with a reagent giving a coloration with nitro-compounds from the partially burnt and unburnt propellant particles. This approach, introduced in 1933 by Teodoro Gonzalez of the Mexico City Police Laboratory, is called dermal nitrate or paraffin test and is no longer used in casework.
Results
A positive result for gunshot residue from SEM-EDX analysis can mean many things. Mainly it indicates that the person sampled was either in the vicinity of a gun when it was fired, handled a gun after it was fired, or touched something that was around the gun when it was fired. (For example: When a person goes to the aid of a victim of a gunshot wound, some gunshot residue particles can transfer from the victim.)
Matching gunshot residue to a specific source
If the ammunition used was specifically tagged in some way by special elements, it is possible to know the cartridge used to produce the gunshot residue. Inference about the source of gunshot residue can be based on the examination of the particles found on a suspect and the population of particles found on the victim, in the firearm or in the cartridge case, as suggested by the ASTM Standard Guide for gunshot residue analysis by scanning electron microscopy/energy dispersiv…
Organic gunshot residue
Organic gunshot residue can be analysed by analytical techniques such as chromatography, capillary electrophoresis, and mass spectrometry.
See also
• Blowback, material drawn into the barrel of a firearm post discharge
External links
• New Scientist, 23 November 2005, "Why we cannot rely on firearm forensics" (subscription required) (Archived copy)
• Scientific Working Group for Gunshot Residue (SWGGSR) http://www.swggsr.org/
• ENFSI EWG Firearms/GSR Working Group http://www.enfsi.eu/about-enfsi/structure/working-groups/firearms-and-gsr