Gunshot residue, forensic analysis and interpretation ppt 03

This presentation contains all about the forensic analysis of gunshot residue, basics of GSR formation, tracing methods, collection and examination methods.

1. Gunshot residue - Forensic Gunshot residue - Forensic
analysis and evaluationanalysis and evaluation
Presented byPresented by
Suryakant Mishra
Asst Professor
Department Zoology and Forensic Science
Kurukshetra University, Kurukshetra

2. Contents
Introduction
Composition of GSR
Location of GSR
Collection Methods
Analysis Methods
1.Chemical test
2. Instrumental techniques
Evaluation of GSR
Significance of Gunshot residue
References

3. Introduction:
The primer is detonated when it is crushed by the force of the firing pin. This
drives hot gases and hot particles into the propellant and ignites it. The
ignited propellant decomposes and forms gaseous products.
Simultaneously, heat, in enormous quantity, is released by this reaction.
The heat generated on ignition of the primer causes the inorganic ingredients
of the primer mixture to vaporize. these vapors re-condense into droplets,
which are further subjected to high pressure and temperature arising from
the burning propellant powder.
The combusted material escapes the weapon through the openings as vapors
and solidified as particulate that varies in shape and size from submicron
to over 100 microns (µm).
Under ideal circumstances it would be expected that all of the propellant
powder would be consumed in the burning process and would be
converted into gases. However, in practice this is not the case because the
whole powder charge is never totally burnt.

4. GSR analysis determines the presence of these materials on the skin and
clothing of subjects and surfaces such as vehicle.
Fig1: Pistol firing showing residue from
muzzle and ejection port
Fig 2: Cloud-like array of lead residues
leaving the muzzle of a revolver

5. The examination and evaluation of GSR is helped to
solve a number of problems:
1.Has the given firearm been fired or not?
2.Has the given ammunition been fired or not?
3.What type of ammunition is used in firing
4.Has the given bullet, pellets, cartridge been fired or not?
5.Who fired the Gun?
6.Did the suspect shoot or suicide?
7.Is the present wound a firearm injury?
•What was the range of firing?
•Is the present firearm wound, an entrance or exit wound?

6. Components of Gunshot residues:
The composition of Gunshot residues depends upon
1.Formulation of primer
2.Formulation of propellant
3.The barrel scrapings
4.The composition of projectile

7. Ammunition primers consist of four basic chemical components:
1)The Initiator — lead styphnate, is standard initiator in modern primer.
Lead azide and mercury fulminate.
2)The Oxidizer — Barium nitrate is most commonly used as an oxidizer in
small-arms ammunition, but barium peroxide, lead nitrate, or lead peroxide
are also used.
3)The Fuel — Antimony sulfide is commonly used as fuel in primers, but
calcium silicide, lead thiocyanate, powdered aluminum, and powdered
zirconium, magnesium, and titanium are also used.
4)The Sensitizing – commonly used sensitizers are tetracene (1-(5-
tetrazolyl)-4-guanyltetrazene hydrate), pentaerythritol tetranitrate,
trinitrotoluene (TNT), and tetryl.

8. Gunpowder: Black powder is composed of 75% potassium nitrate,
15% sulfur, and 10% charcoal.
Smokeless Powder:

Single base – Nitrocellulose
Double base: Nitrocellulose +Nitroglycerine
All smokeless powders, in addition to explosive ingredients, contain a number
of additives. These additives fulfill the role as stabilizers, plasticizers, flash
inhibitors, coolants, moderantes, surface lubricants.
Combustion product of Black powder - carbonmonooxide, carbon dioxide,
sulphates, carbonates, thiosulphate, sulphides, Potassium.

9. Common stabilizers: - diphenylamine, the centralites, and resorcinol.
Diphenylamine (DPA) is the most common stabilizer used in smokeless
powders, especially in single base powders.
Plasticizers:- glyceryl triacetate (triacetin), dimethyl phthalate, diethyl
phthalate, and dibutyl phthalate.
Flash suppresser: - Dinitrotoluene is used as a flash suppresser in some
smokeless powders. Nitroguanidine fulfills the same role. The role of a flash
suppresser is to produce nitrogen gas to dilute the muzzle gases.
Lubricants: - The powder grains are also coated with graphite .

10. The detectable inorganic components of GSR:
Lead
Barium
Antimony
Copper from jacket of bullet
Iron from barrel
Nitrates and nitrite
Zinc from the Jacket
Nickel from nickel coated shells
The detectable organic components of Gunshot residues:
Nitrocellulose- unburned and semi-burned
Nitroglycerine
Diphenylamine-stabilizer
(DNT) di-nitro toluene, used as plasticizer
Bullet lubricants
Bullets:
Core of bullet:
Lead + antimony 85%+15, lead+Tin (Sn) (90-98%+2-10%).
Jacket of bullet -copper alloys, with Zn, or Tin; Steel

11. Location of Gunshot residues:
The basic principle of trace and transfer evidence is the Locard Exchange
Principle.
Detection of Gunshot residues:
1.Residues should initially be observed and evaluated by the unaided eye
and with a low power stereomicroscope.
2.X – ray photography
3.IR- photography-Infrared imaging may be used to visualize heavy soot
on dark or bloody clothing or on multicoloured surfaces.
4.Chemical methods

12. Fig3: Visualization of GSR by IR Photography on Multicolor
bloody surface

13. Collection of Gunshot residues
Collection of inorganic gunshot residues:
•Wet Methods: 5% nitric acid is commonly used for collecting inorganic
contents of GSR,
•Tape lifting: This technique has mainly been used to sample inorganic
residues for SEM analysis.
Collection of Organic Residues
•Swabbing: Swabbing is the most common technique for collecting organic
residues.
Acetone is most suitable solvent for collection of organic residues, other
solvent are cyclohexane and ethanol.
•Vacuum Lifting
It is commonly used technique for collecting organic gunshot residues from
clothing. Clothing debris is vacuumed on to a filter disc, and then the filter is
extracted with solvent to recover the organic gunshot residues. Its main
advantages are its ease of operation and the fact that a larger area can be
sampled within a short time.

14. Fig4: Collection of GSR by Adhesive tape
lifting method

15. Sample pretreatment:
In many chromatographic analyses, the analytical systems are
able to detect pure standards of organic gunshot residues down
to low nanogram levels but such sensitivity cannot be achieved
with extracts from handswabs or vacuumed clothing samples.
This problem arises because such extracts are substantially
contaminated with lipids and other co-extracted materials which
result in deterioration of the separation column and the detector.

16. Analytical Methods
1. Chemical tests:
Griess reagent test: - Griess reagent which is based on the formation of
a diazonium salt when nitrite in acid solution reacts with a primary
aromatic amine. A common example is a solution of alpha-
naphthylamine and sulfanilic acid in acetic acid. The sulfanilic acid
reacts with nitrites to yield a diazonium ion which then couples with
alpha-naphthylamine to produce a red azo dye

17. Figure 5 : red /orange colour
showing in lower image by Griess
Reagent test
Sodium Rhodizonate Test
This test is commonly used to detect lead residues from exhibits,
1.Weak solution of sodium rhodizonate in distilled water apply on sample ,
in the presence of lead it gives pink colour , and to confirm the lead residues
the area can spray with dil HCl solution .
2.If pink color turn blue then the presence of lead is confirmed.
Detection limit of the modified Griess reagent is reported to be 0.1
microgram.

18. Note: Modified Griess Test and the Sodium Rhodizonate Test yield
positive reactions to nitrite compounds and lead respectively, whether or
not the source is in fact from a gunshot
Fig 6: Colour reaction sodium
rhodizonate test
Thin Layer Chromatography
Solvent system: toluene/petroleum ether/ethyl acetate (12:12:1).
Visualizing reagent- Griess reagent
Fig 7: Reaction colour after applying dil HCl

19. Instrumental analysis of Gunshot residues
1. Scanning Electron Microscopy with an Energy dispersive X-ray analyzer SEM-EDX
1.Technique is specific for characteristics and morphological analysis of
Inorganic Gunshot residue particles
2.Particle by particle studies is possible
3.It is non destructive technique
4.It provides high resolution and magnification in excess of 1000000X.
The SEM – EDX is usually equipped to detect electrons generated by
two different processes for imaging, secondary and backscattered, and
with X-rays for compositional analysis.

20. In scanning electron microscopy a fine beam of electron is focused on
material under study. The electron beam produces the following effect:
1.When beam of primary electron collide with specimen, some electrons
are reflected back (back scatter), the image obtained from these electrons
provides 3D image of particle.
2.When the primary electron beam hits the specimen, atoms ionized by the
forced emission of electrons. The specimen electrons emitted from the
sample are referred to as secondary electrons.
3.It generates X-rays- the generated X-rays are used to find out the
elemental composition of particles.

21. A View of Scanning Electron Microscope

22. SEM image of Gunshot residue particle
5
EDS spectra of “unique” gunshot residue particle showing the identification
of multiple peaks for Pb , Sb and Ba
5

23. SEM-EDX Spectra and spheroid shape of lead particle [9]

24. SEM-EDX spectrum from gunshot residues of lead free
primer ammunition
8

25. Uniqueness of Composition:
When Pb, Sb, and Ba combine into a single particle, it is defined as
being unique to GSR, since there is no other known source of this
compound. Each individual element or other combinations of these
elements with high temperature features are classified as characteristic
of GSR
Unique: Pb-Sb-Ba
Characteristics:
Pb-Sb
Pb-Ba
Sb-Ba
Sb
Ba
Ba-Ca-Si (with trace S)

26. Examples of some of the chief commercial or industrial uses of Pb,
Sb, and Ba are as follows.
Lead (Pb) — melting point 327°C
Storage batteries, solder, bearing metals, gasoline, bullets, shot, paint, shielding
sheet, cable coverings, glass, matches, dyes, and pyrotechnics.
Antimony (Sb) — melting point 440°C
Hardening alloys (lead base, etc.), paint pigment, safety matches, bearings,
pewter utensils, brake pads, and pyrotechnics.
Barium (Ba) — melting point 850°C
Deoxidizing alloys of tin, copper (Cu), Pb, and zinc (Zn), radiography, in heat-
treating baths for tempering of steel, in laser crystals, dyes, inks, leather
tanning, photographic chemicals, insecticides, paper products, and
pyrotechnics.

27. The decisive factors in the identification of GSR are the specific
composition, morphology, and chemistry of the particle, as well as the
characterization of the overall population of particles detected on the same
sample.
Morphology of Gunshot residues particle
Size of particles
Minimum Requirement for positive identification

28. Graphite Furnace Atomic Absorption Spectroscopy
(GFAAS):
This is a very sensitive quantitative analysis method for trace elements
of primer residue, such as Pb, Sb, Ba etc
AAS works on a very simple principle. An element absorbs the
radiation of the same wave length as it emits when exited.
The absorption signal measured during the atomization stage is
proportional to the amount of analyte element s in the sample.

29. Inductively Coupled Plasma-Mass Spectroscopy (ICP-
MS)
Inductively Coupled Plasma-Mass Spectroscopy (ICP-MS) is a bulk
method of analysis used to measure trace amounts of Pb, Ba, and Sb in
primer residue samples.
It operates by coupling an argon plasma to a radio frequency (RF)
electromagnetic field at atmospheric pressure. Samples are usually
introduced in liquid form. Detection limits are usually in the parts-per-
billion level.

30. Organic components of gunshot residues such as nitrocellulose,
nitroglycerine, diphenylamine ,dintrotoluene etc can be detected by present
sophisticated techniques and these may be taken as evidence of the
presence of gunshot residues.
Ethyl centralite was recommended by Mach et al.[7] as the most
characteristic material in smokeless powders, with 2,4-dinitrotoluene being
the second most characteristic material
1.High performance Liquid chromatography with mass spectrometry
(HPLC-MS)
2. Capillary Electrophoresis (CE):
Micellar Electrokinetic Capillary Electrophoresis (CE) is a bulk method
of analysis that is designed to separate and detect organic and explosive
material components.
Techniques for organic Gunshot residues

31. Limitation in Organic residues:
1.Nitrocellulose is, also in widespread used in many consumer
products such as lacquers and paints.
2.Nitroglycerine is not only used in double and triple base
gunpowder’s but also in pharmaceutical products in which its role is
as a cardiac stimulant.

32. Significances of Gunshot residues problems
Identification of Shooter:
Many variation play parts in the identification of the hand that fired the
shot, the major variables are
•The nature of Firearm
•The length of barrel
•The time elapsed since firing
Distribution of GSR on hands:
1.GSR particle on the back of the hand (right or left)
2.GSR particles from the back of the both hands
3.GSR particles on both side of both hands
4.GSR particles on the palms of the both hands

34. List of generally accepted particle for GSR
identification in case of shooter identification:
Pb Sn Ba Sb- positive GSR
Pb Ba Sb- positive GSR
Pb Sn Sb- positive GSR
Sn Ba Sb- positive GSR
Pb Sn Ba - positive GSR
Sb Ba- indicative
Sb Pb-indicative
Ba Pb-indicative
Sb Sn-indicative
Pb- indicative

35. References:
1.A. J. Schwoeble and David L. Exline. Current Methods in Forensic
Gunshot Residue Analysis, 2000, CRC Press London.
2.Peter F. Mahoney, James M. Ryan, Adam J. Brooks and C.William
Schwab. Ballistic Trauma, a practicle Guid, 2
nd
edt. Springer.
3.Stahling S and Karlsson T. A method for collection of gunshot residues
from skin and other surfaces. J Forensic Sci. 2000; 45(6):1299–1302
4.Brain J Heard. Handbook of Firearms and Ballistics; 2
nd
edt.2008, John
Wiley-Blackwell Ltd UK.
5.Romolo FS, and Margot P. Indentification of Gunshot residues a critical
review, Forensic Sci.Intern.119 (2001)195-211.

36. 6. Vinokurov A, Zelkowicz, Wolf E, Zeichner. The influence of a possible
contamination of the victim’s clothing by gunpowder residue on the
estimation of shooting distance. Forensic Sci. Intern. 194 (2010) 72–
76
7. Hsien-Hui Meng and Hsei-Chang Lee. Elemental analysis of primer
mixtures and gunshot residues from handgun cartridges commonly
encountered in Taiwan, Forensic Science Journal. 6 (1) 2007 : 39-54
8. Martiny A, CamposAP, Sader MS, Pinto M A. SEM/EDS analysis and
characterisation of gunshot residues from Brazillion lead free
ammunition. J Forensic Sci. 177 (1) 2008: 9-17.
9. Coumbaros J, Kirkberide Kk P. klass G., Skinner W., Characterization
of 0.22 caliber rimfire gunshot residues by time-of-flite secondary
ion mass spectrometry: a preliminary study. Forensic Sci. Intern.
119(2001): 72-81.

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