Gun Shot Residue Analysis

This presentation is about the Gun Shot Residue which is a prime evidence in the investigation of crimes involving a use of firearm. It will inform the viewer about the composition, relevance and various chemical and instrumental methods employed for its analysis.

1. University of Lucknow Department of Anthropology Forensic Science Gun Shot Residue Prepared By Mohd Hamza

2. Gun Shot Residue What is GSR? Production and dependence upon Range. Where is it found? Its Composition and Classification. How is it collected? Methods for its detection and analysis. Forensic Relevance.

3. What is Gun Shot Residue? Gun Shot Residue (GSR) also known as CDR (cartridge discharge residue) and FDR (firearm discharge residue) comprises gases, non-volatile, visible and invisible particles which may be unburnt or partially burnt coming from Barrel, Primer, Propellant, Cartridge, Bullet and Firearm. There detection location analysis plays an important role in investigative procedures involving usage of any type of firearm.

4. Where is it found? GSR may be looked for On the hands - mainly present on thumb, trigger finger and web of hand On the clothes of the victim, if the human being is the target Intermediate targets may also have GSR depositions Inside of cartridge cases and barrel may have GSR. In addition outside surface of barrel can also be examined for GSR. Fired projectiles may also be examined for gunshot residue.

5. Production and dependence upon Range. Distant Range In the case of distant-range firing there will be no GSR like blackening, scorching and tattooing as well as metallic chips around the hole of entrance. All of them will not appear and remain absent. However , during the passage of a bullet through the rifled barrel and through a defective, roughened or country made weapons (also termed improvised weapons), small fragments of metal are cut and propelled in the direction in which projectiles are ejected. In view of the fact that these particles are heavier than the powder grains they travel longer distance beyond the maximum distance to which powder grains are ejected.

6. Close Range In close range firing, dust ring, burning, blackening and tattooing appears as GSR on the target as shown in the figure below. The burning of skin is accompanied in by the track shown in the figure due to its reaction with carbon monoxide which is also a product of combustion (GSR). In case of contact firing, it is the entry which has projectiles and other GSR in the track of the hole in additions to the above mentioned locations GSR can be located at the following places or articles : Articles around the target or around the shooter or both, depending upon the nature of firing, may contain GSR.

7. Clothes and other garments of the victim, which act like intermediate targets, may have GSR on them. The GSR particles are dispersed in the air. Being light particles, they continue in the air for a long time. They may be transferred to a surface, which comes in contact with air, or surface, which already has GSR. Intermediate targets, other than clothes, may also have GSR when a projectile hits a glass windowpane or a wooden door. The holes created by a bullet in a glass pane or wooden door would carry especially the GSR, load particles, and many others depending on the cartridge cases and primer.

8. Contact Range While a weapon is fired, and the muzzle end is expected to touch the target it is termed contact range. When the contact is tight and pressing the surface of a target uniformly and close, the skin surrounding the perforation is not tattooed or blackened with embedded powder grains as in a case of close-range shot indicating absence of GSR, but this may not happen, always. Occasionally , some burned and unburned powder grains may get deposited on the skin in and around the margins of entrance wound. It is just possible that the weapon may be lifted, on one side due to manufacturing defect in country made weapon or due to careless handling by the shooter or efforts made by victim. To escape an attack, resulting in losing of light contact giving rise to escape or burned and unburned powder grain and their deposition on the skin. In a tight and proper contact, all the GSR as well as ammunition would be driven into track made by the ammunition through the entrance hole.

9. Hands of shooter- When a firearm is fired it not only shoots GSR and projectile forward but some of the particles are backfired and thereby spread on the hands of the person shooting it. Clothes- Clothes of the victim lie as the first line between victim’s body and projectile and the incoming GSR also the particles stuck on the projectile get wiped of as it enters through the clothes due to motion and friction of the projectile.

10. Intermediate Target- GSR may also be looked upon the intermediate materials bullet passes through before reaching the final target in many of the cases glass panes are a commonly found intermediate targets. Barrel- If not manipulated can be a source of GSR as well it may be found inside or outside the barrel.

11. Composition and Classification. GSR Inorganic Organic Bullet- Lead. Nitrocellulose Barrel- Iron Nitro-glycerine Primer- Antimony, Barium, Lead Lubricants (Paraffin) Propellant- Nitrate, Nitrite, CO, C. Cartridge- Nickel, Zinc, Copper

12. How it collected? Wet Methods A cellophane sheet is impregnated with acetic acid, after impregnation the same is pressed against the site. It will pick up bad particles. A solution of cellulose acetate is applied bearing the GSR. When it gets dried up it may be peeled off and the gunshot residues will be picked up by the cast. The site bearing the powder marks is sprayed with a colloidal solution. The film is reinforced with nylon fibres. The reformed film that picks up the GSR is peeled off on drying. The residues in the barrel are collected by washing the same with hot distilled water. The washings are tested for constituents of the gun powder residues

13. Dry Methods Use of adhesive tapes. An inert adhesive tape (or an adhesive aluminium tape) is pressed against the site bearing the GSR many a times to pick up the desired GSR which can then be subsequently selected for examination. Technique of Swabbing- A clean piece of cloth or a filter paper is moistened with an organic solvent, which may by acetone, alcohol or ether and the site suspected of containing GSR is swabbed. The swabs are collected and extracted. Vacuum Lifting Technique- This technique is especially suitable for collecting of GSR from clothes. The material deposited on the filter dust is extracted with a suitable solvent for further processing.

14. Infrared Detection Sometimes the lack of colour contrast between the powder and the garment or presence of heavily encrusted deposits of blood can obscure the visual detection of gun powder. Often an infrared photograph of suspect area, on the garment, overcomes such the problem. Fabric bearing GSR marks invisible to naked eyes due to colour contrast Same Fabric under IR Photography

15. Methods of Collection and Analysis. Chemical Tests Instrumental Tests Sodium Rhodizonate Scanning Electron Microscope Walker Test Transmission Electron Microscope Neutron Activation Analysis Marshall Test X-Ray Florescence Tewari Test Lunge’s Reagent

16. Chemical Tests Sodium Rhodizonate Filter paper moistened with 0.1 HCl is pressed against the wound. It is then blow dried. Spotted with Sodium Rhodizonate paper gives orange colouration indicating presence of Lead. Solution of HCl is then again sprayed until orange colour disappears. Gradual appearance of purple spots confirms the presence of Lead.

17. Walker Test Photographic paper is desensitised with a hypo fixer and then immersed in 5% 2-Napthylammine-4,8-sulphonic acid. Cloth wetted with 20% Acetic Acid is then placed over the “Sample Cloth”, on top of which prepared photographic paper is placed and covered with a dry cloth. Warmed and ironed for 5 minutes. Bright red colouration gives presence of Nitrite.

18. Marshal Test Desensitized photography paper is immersed in 0.5% Sulphanillic Acid and then dried. It is then immersed in 0.5% solution of N-alpha- Napthylethylienediammine Hydrochloride in Methanol. Cloth wetted with 20% acetic acid is placed under the sample clothe and then on top is placed photographic paper and whole preparation is covered with a dry cloth and ironed for 5 minutes. Purple spots on purple background indicates presence of Nitrites. Rinsed in distilled water to remove background colour. Immersed in Methanol to give orange colour, confirming presence of Nitrites.

19. Tewari Test 1gm of Antazoline is dissolved in 50ml of distilled water. 45ml of conc. HCl is added until white ppt is dissolved. Filter paper soaked in Acetone is pressed against wound. Air dried and sprayed heavily with the Antazoline solution. Bright yellow spots indicate presence of Nitrites.

20. Dermal Nitrate Test 0.25% solution of Diphenylamine is sprayed over paraffin cast of perpetuator’s hands. Blue colour indicates presence of Nitrates.

21. Instrumentation Methods Scanning Electron Microscope Scanning electron microscope was first developed by Knoll and Zworykim in 1942. The working principle of the instrument is that a high energy electron beam is projected upon the surface of the given sample which scans the sample and image is projected upon a screen ( PbS coated) It consists of following components.

22. Electron Gun- usually made up of tungsten shoots the beam of electron. Condenser Lenses- these are electromagnetic lenses that adjust the illumination or magnification by altering the velocity of electrons, by increasing the velocity we decrease the wavelength thereby increasing its magnification, resolution and depth of focus. Scanning Coils- these are current carrying metallic coils that alter the movement of electrons by altering the flow of current through them. Projection Lens- this is the lens which has been replaced with the eyepiece of a light microscope.

23. Detectors- these detect how the electrons interact with the sample. Objective Lens- inserted to adjust the aperture. Fluorescent Screen- This is where we obtain the final image it is coated with Lead Sulphide. Transmission Electron Microscope Designed in 1931 by Luska and Max. Its working principle is same as SEM just that it requires sample in a form very thin layer and it is not capable to give a 3D image. It is about 1000x times stronger than light electrons.

24. Neutron Activation Analysis It is based on the principal that when neutrons are bombarded upon any substance, a certain amount of radioactivity is induced in that material. The measure of this induced radioactivity can provide qualitative and quantitative data for that particular material. It was developed by Havsi and Levi in 1936 and is also termed as referee method as it gives reference data for other tests. It gives result in the unit of particles per billion. Almost 100000 samples undergo NAA each day.

25. Process Neutrons are bombarded upon the sample thereby converting it into a compound nucleus which is highly unstable. Compound Nucleus in an attempt to attain stability release Prompted Gamma Rays (which come under PGNAA) and passes through an intermediate state of being radioactive. This radioactive nucleus radiate Delayed Gamma Rays. These Delayed Gamma Radiations come under DGNAA and 70% of the materials show this property. The energy of DGR is directly proportional to Radioactivity of the material. Curve between energy of Gamma Rays and Radioactivity is plotted and gives qualitative and quantitative data. Incident neutron Target Nucleus Compound Nucleus Radioactive Nucleus Product Nucleus Prompted Gamma Rays Delayed Gamma Rays Beta Particles

26. X-Ray Florescence Florescence is a phenomenon in which some materials absorb low wavelength (UV) Electromagnetic Radiations and radiate a part of them converted into a spectra of visible light of various wavelength and colour. In case of X-ray fluorescence the incidents X-ray as well as fluorescent radiation both are invisible to the human eyes as both the radiation incident and fluorescence lie in the invisible spectrum, but the basis fact remains the same meaning thereby that in the incident X-ray radiation will be of lower wavelength and fluorescence radiation of higher wave length . The sample to be analysed for elemental composition is placed in the path of X-ray beam which will get absorbed by the sample. The absorbing atoms get excited and emit X-ray of characteristic wavelength of elements present in the absorbing material and this process is known as fluorescence. As the wavelength of the fluorescence is characteristic of excited atoms of particular elements, measure of this wave length would enable one to identify the fluorescing element . For calculating wavelength Bragg’s Law is applied which is λ = 2 d Sin θ θ θ θ θ d – Crystal Lattice

27. Forensic Relevance Range Determination. Crime Scene Reconstruction. Identification of Cartridge and Firearm. Identification of Suspect. Analysis and linking of secondary evidences (intermediate targets).

28. Thank You.