Gunshot residue
Encyclopedia
Gunshot residue is principally composed of burnt and unburnt particles from the explosive primer, the propellant
, as well as components from the bullet
, the cartridge
case and the firearm
used. There are authors who use other definitions, such as cartridge discharge residue (CDR) or firearm discharge residue (FDR).
Gunshot Residue (GSR) is the residue that gets deposited on the hands of the shooter after the bullet has been fired. It may or may not have some burnt, unburnt or semi-burnt particles.
GSR can be very helpful in connecting the firearm to the culprit, establishing the identity of the shooter and in some cases may help in eliminating the probability when the number of suspect is more.
Gunshot residue can travel out from the gun to distances of 3–5 feet (0.3–1.5 meters) or even farther. At the farthest distance, only a few trace particles may be present. This information can be useful in determining if someone was involved in the firing of the gun. Close to the gun barrel, the residue deposits more heavily on surfaces like skin and clothing, to the point of being visible as a dark stain. Detection of a significant amount of residue, therefore, is a powerful piece of forensic evidence that the particular person was very near to, even holding, the gun when it discharged.
In 1971 John Boehm presented some micrographs of GSR particles found during the examination of bullet
entrance holes using a scanning electron microscope
. If the scanning electron microscope
is equipped with an energy-dispersive X-ray spectroscopy
detector, the chemical elements present in such particles, mainly lead
, antimony
and barium
, can be identified.
In 1979 Wolten et al. proposed a classification of GSR following compositional criteria, morphology
and size. Four compositions were considered “characteristic”: lead
, antimony
and barium
; barium
, calcium
and silicon
; antimony
and barium
. The authors proposed some rules about the chemical elements which could also be present in these particles.
Wallace and McQuillan published a new classification of the GSR particles in 1984. They called “unique” particles the ones containing lead
, antimony
and barium
, or the ones containing antimony
and barium
. Also for Wallace and McQuillan in these particles only some chemical elements could be present.
In the latest ASTM Standard Guide for GSR analysis by Scanning Electron Microscopy/Energy Dispersive X-ray
Spectrometry 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 if a particle is characteristic of or consistent with GSR is by its elemental profile. An approach to the identification of particles characteristic of or consistent with GSR is to compare the elemental profile of the recovered particulate with that collected from case-specific known source items, such as the recovered weapon
, cartridge
cases or victim-related items whenever necessary. This approach was called ‘‘case by case’’ by Romolo and Margot in an article published in 2001. In 2010 Dalby et al. published the latest review on the subject and concluded that the adoption of a ‘‘case by case’’ approach to GSR analysis must be seen as preferable, in agreement with Romolo and Margot.
In light of similar particles which can be produced from extraneous sources, both Mosher et al. (1998) and Grima et al. (2011) presented evidence of pyrotechnic particles which can be mistakenly identified as GSR. Both publications highlight that certain markers of exclusion and reference to the general population of collected particulate can help the expert in designating GSR-similar particles as firework
-sourced.
Particle analysis by scanning electron microscope
equipped with an energy-dispersive X-ray spectroscopy
detector can be the most powerful tool for forensic scientists to determine the proximity to a discharging firearm and/or the contact with a surface exposed to GSR (firearm
, spent cartridge
case, target hole), if proper attention is paid to avoid secondary gunshot residue transfer from officers onto subjects or items to be tested for GSR, and to avoid contamination
in the laboratories.
Organic
gunshot residue can be analysed by analytical techniques such as chromatography
, capillary electrophoresis
, and mass spectrometry
.
Propellant
A propellant is a material that produces pressurized gas that:* can be directed through a nozzle, thereby producing thrust ;...
, as well as components from the bullet
Bullet
A bullet is a projectile propelled by a firearm, sling, or air gun. Bullets do not normally contain explosives, but damage the intended target by impact and penetration...
, the cartridge
Cartridge (firearms)
A cartridge, also called a round, packages the bullet, gunpowder and primer into a single metallic case precisely made to fit the firing chamber of a firearm. The primer is a small charge of impact-sensitive chemical that may be located at the center of the case head or at its rim . Electrically...
case and the firearm
Firearm
A firearm is a weapon that launches one, or many, projectile at high velocity through confined burning of a propellant. This subsonic burning process is technically known as deflagration, as opposed to supersonic combustion known as a detonation. In older firearms, the propellant was typically...
used. There are authors who use other definitions, such as cartridge discharge residue (CDR) or firearm discharge residue (FDR).
Gunshot Residue (GSR) is the residue that gets deposited on the hands of the shooter after the bullet has been fired. It may or may not have some burnt, unburnt or semi-burnt particles.
GSR can be very helpful in connecting the firearm to the culprit, establishing the identity of the shooter and in some cases may help in eliminating the probability when the number of suspect is more.
Gunshot residue can travel out from the gun to distances of 3–5 feet (0.3–1.5 meters) or even farther. At the farthest distance, only a few trace particles may be present. This information can be useful in determining if someone was involved in the firing of the gun. Close to the gun barrel, the residue deposits more heavily on surfaces like skin and clothing, to the point of being visible as a dark stain. Detection of a significant amount of residue, therefore, is a powerful piece of forensic evidence that the particular person was very near to, even holding, the gun when it discharged.
In 1971 John Boehm presented some micrographs of GSR particles found during the examination of bullet
Bullet
A bullet is a projectile propelled by a firearm, sling, or air gun. Bullets do not normally contain explosives, but damage the intended target by impact and penetration...
entrance holes using a scanning electron microscope
Scanning electron microscope
A scanning electron microscope is a type of electron microscope that images a sample by scanning it with a high-energy beam of electrons in a raster scan pattern...
. If the scanning electron microscope
Scanning electron microscope
A scanning electron microscope is a type of electron microscope that images a sample by scanning it with a high-energy beam of electrons in a raster scan pattern...
is equipped with an energy-dispersive X-ray spectroscopy
Energy-dispersive X-ray spectroscopy
Energy-dispersive X-ray spectroscopy is an analytical technique used for the elemental analysis or chemical characterization of a sample. It relies on the investigation of an interaction of a some source of X-ray excitation and a sample...
detector, the chemical elements present in such particles, mainly lead
Lead
Lead is a main-group element in the carbon group with the symbol Pb and atomic number 82. Lead is a soft, malleable poor metal. It is also counted as one of the heavy metals. Metallic lead has a bluish-white color after being freshly cut, but it soon tarnishes to a dull grayish color when exposed...
, antimony
Antimony
Antimony is a toxic chemical element with the symbol Sb and an atomic number of 51. A lustrous grey metalloid, it is found in nature mainly as the sulfide mineral stibnite...
and barium
Barium
Barium is a chemical element with the symbol Ba and atomic number 56. It is the fifth element in Group 2, a soft silvery metallic alkaline earth metal. Barium is never found in nature in its pure form due to its reactivity with air. Its oxide is historically known as baryta but it reacts with...
, can be identified.
In 1979 Wolten et al. proposed a classification of GSR following compositional criteria, morphology
Morphology
Morphology may mean:*Morphology , the study of the structure and content of word forms*Morphology , the study of the form or shape of an organism or part thereof...
and size. Four compositions were considered “characteristic”: lead
Lead
Lead is a main-group element in the carbon group with the symbol Pb and atomic number 82. Lead is a soft, malleable poor metal. It is also counted as one of the heavy metals. Metallic lead has a bluish-white color after being freshly cut, but it soon tarnishes to a dull grayish color when exposed...
, antimony
Antimony
Antimony is a toxic chemical element with the symbol Sb and an atomic number of 51. A lustrous grey metalloid, it is found in nature mainly as the sulfide mineral stibnite...
and barium
Barium
Barium is a chemical element with the symbol Ba and atomic number 56. It is the fifth element in Group 2, a soft silvery metallic alkaline earth metal. Barium is never found in nature in its pure form due to its reactivity with air. Its oxide is historically known as baryta but it reacts with...
; barium
Barium
Barium is a chemical element with the symbol Ba and atomic number 56. It is the fifth element in Group 2, a soft silvery metallic alkaline earth metal. Barium is never found in nature in its pure form due to its reactivity with air. Its oxide is historically known as baryta but it reacts with...
, calcium
Calcium
Calcium is the chemical element with the symbol Ca and atomic number 20. It has an atomic mass of 40.078 amu. Calcium is a soft gray alkaline earth metal, and is the fifth-most-abundant element by mass in the Earth's crust...
and silicon
Silicon
Silicon is a chemical element with the symbol Si and atomic number 14. A tetravalent metalloid, it is less reactive than its chemical analog carbon, the nonmetal directly above it in the periodic table, but more reactive than germanium, the metalloid directly below it in the table...
; antimony
Antimony
Antimony is a toxic chemical element with the symbol Sb and an atomic number of 51. A lustrous grey metalloid, it is found in nature mainly as the sulfide mineral stibnite...
and barium
Barium
Barium is a chemical element with the symbol Ba and atomic number 56. It is the fifth element in Group 2, a soft silvery metallic alkaline earth metal. Barium is never found in nature in its pure form due to its reactivity with air. Its oxide is historically known as baryta but it reacts with...
. The authors proposed some rules about the chemical elements which could also be present in these particles.
Wallace and McQuillan published a new classification of the GSR particles in 1984. They called “unique” particles the ones containing lead
Lead
Lead is a main-group element in the carbon group with the symbol Pb and atomic number 82. Lead is a soft, malleable poor metal. It is also counted as one of the heavy metals. Metallic lead has a bluish-white color after being freshly cut, but it soon tarnishes to a dull grayish color when exposed...
, antimony
Antimony
Antimony is a toxic chemical element with the symbol Sb and an atomic number of 51. A lustrous grey metalloid, it is found in nature mainly as the sulfide mineral stibnite...
and barium
Barium
Barium is a chemical element with the symbol Ba and atomic number 56. It is the fifth element in Group 2, a soft silvery metallic alkaline earth metal. Barium is never found in nature in its pure form due to its reactivity with air. Its oxide is historically known as baryta but it reacts with...
, or the ones containing antimony
Antimony
Antimony is a toxic chemical element with the symbol Sb and an atomic number of 51. A lustrous grey metalloid, it is found in nature mainly as the sulfide mineral stibnite...
and barium
Barium
Barium is a chemical element with the symbol Ba and atomic number 56. It is the fifth element in Group 2, a soft silvery metallic alkaline earth metal. Barium is never found in nature in its pure form due to its reactivity with air. Its oxide is historically known as baryta but it reacts with...
. Also for Wallace and McQuillan in these particles only some chemical elements could be present.
In the latest ASTM Standard Guide for GSR analysis by Scanning Electron Microscopy/Energy Dispersive X-ray
X-ray
X-radiation is a form of electromagnetic radiation. X-rays have a wavelength in the range of 0.01 to 10 nanometers, corresponding to frequencies in the range 30 petahertz to 30 exahertz and energies in the range 120 eV to 120 keV. They are shorter in wavelength than UV rays and longer than gamma...
Spectrometry particles containing lead
Lead
Lead is a main-group element in the carbon group with the symbol Pb and atomic number 82. Lead is a soft, malleable poor metal. It is also counted as one of the heavy metals. Metallic lead has a bluish-white color after being freshly cut, but it soon tarnishes to a dull grayish color when exposed...
, antimony
Antimony
Antimony is a toxic chemical element with the symbol Sb and an atomic number of 51. A lustrous grey metalloid, it is found in nature mainly as the sulfide mineral stibnite...
and barium
Barium
Barium is a chemical element with the symbol Ba and atomic number 56. It is the fifth element in Group 2, a soft silvery metallic alkaline earth metal. Barium is never found in nature in its pure form due to its reactivity with air. Its oxide is historically known as baryta but it reacts with...
, and respecting some rules related to the morphology
Morphology
Morphology may mean:*Morphology , the study of the structure and content of word forms*Morphology , the study of the form or shape of an organism or part thereof...
and to the presence of other elements are considered characteristic of GSR. The most definitive method to determine if a particle is characteristic of or consistent with GSR is by its elemental profile. An approach to the identification of particles characteristic of or consistent with GSR is to compare the elemental profile of the recovered particulate with that collected from case-specific known source items, such as the recovered weapon
Weapon
A weapon, arm, or armament is a tool or instrument used with the aim of causing damage or harm to living beings or artificial structures or systems...
, cartridge
Cartridge (firearms)
A cartridge, also called a round, packages the bullet, gunpowder and primer into a single metallic case precisely made to fit the firing chamber of a firearm. The primer is a small charge of impact-sensitive chemical that may be located at the center of the case head or at its rim . Electrically...
cases or victim-related items whenever necessary. This approach was called ‘‘case by case’’ by Romolo and Margot in an article published in 2001. In 2010 Dalby et al. published the latest review on the subject and concluded that the adoption of a ‘‘case by case’’ approach to GSR analysis must be seen as preferable, in agreement with Romolo and Margot.
In light of similar particles which can be produced from extraneous sources, both Mosher et al. (1998) and Grima et al. (2011) presented evidence of pyrotechnic particles which can be mistakenly identified as GSR. Both publications highlight that certain markers of exclusion and reference to the general population of collected particulate can help the expert in designating GSR-similar particles as firework
Fireworks
Fireworks are a class of explosive pyrotechnic devices used for aesthetic and entertainment purposes. The most common use of a firework is as part of a fireworks display. A fireworks event is a display of the effects produced by firework devices...
-sourced.
Particle analysis by scanning electron microscope
Scanning electron microscope
A scanning electron microscope is a type of electron microscope that images a sample by scanning it with a high-energy beam of electrons in a raster scan pattern...
equipped with an energy-dispersive X-ray spectroscopy
Energy-dispersive X-ray spectroscopy
Energy-dispersive X-ray spectroscopy is an analytical technique used for the elemental analysis or chemical characterization of a sample. It relies on the investigation of an interaction of a some source of X-ray excitation and a sample...
detector can be the most powerful tool for forensic scientists to determine the proximity to a discharging firearm and/or the contact with a surface exposed to GSR (firearm
Firearm
A firearm is a weapon that launches one, or many, projectile at high velocity through confined burning of a propellant. This subsonic burning process is technically known as deflagration, as opposed to supersonic combustion known as a detonation. In older firearms, the propellant was typically...
, spent cartridge
Cartridge (firearms)
A cartridge, also called a round, packages the bullet, gunpowder and primer into a single metallic case precisely made to fit the firing chamber of a firearm. The primer is a small charge of impact-sensitive chemical that may be located at the center of the case head or at its rim . Electrically...
case, target hole), if proper attention is paid to avoid secondary gunshot residue transfer from officers onto subjects or items to be tested for GSR, and to avoid contamination
Contamination
Contamination is the presence of a minor and unwanted constituent in material, physical body, natural environment, at a workplace, etc.-Specifics:"Contamination" also has more specific meanings in science:...
in the laboratories.
Organic
Organic compound
An organic compound is any member of a large class of gaseous, liquid, or solid chemical compounds whose molecules contain carbon. For historical reasons discussed below, a few types of carbon-containing compounds such as carbides, carbonates, simple oxides of carbon, and cyanides, as well as the...
gunshot residue can be analysed by analytical techniques such as chromatography
Chromatography
Chromatography is the collective term for a set of laboratory techniques for the separation of mixtures....
, capillary electrophoresis
Capillary electrophoresis
Capillary electrophoresis , also known as capillary zone electrophoresis , can be used to separate ionic species by their charge and frictional forces and hydrodynamic radius. In traditional electrophoresis, electrically charged analytes move in a conductive liquid medium under the influence of an...
, and mass spectrometry
Mass spectrometry
Mass spectrometry is an analytical technique that measures the mass-to-charge ratio of charged particles.It is used for determining masses of particles, for determining the elemental composition of a sample or molecule, and for elucidating the chemical structures of molecules, such as peptides and...
.
External links
- New ScientistNew ScientistNew Scientist is a weekly non-peer-reviewed English-language international science magazine, which since 1996 has also run a website, covering recent developments in science and technology for a general audience. Founded in 1956, it is published by Reed Business Information Ltd, a subsidiary of...
, 23 November 2005, "Why we cannot rely on firearm forensics"