Gunshot Residue Aanalysis Essay Example

who fired the gun should be approached cautiously because any body part or object near the fired gun may have residue that appears consistent with being the shooter. Specific elements like Zinc (Zn) and Copper (Cu) can also be detected in the cartridge case, slug, and slug coating.

There are three types of GSR atoms that exhibit specific shapes: regular ellipsoid of revolutions, irregular atoms, and atoms that form a bed of lead around a central nucleus. It is crucial to promptly aggregate GSR as the grounds can easily be compromised by rinsing. Once examined, it usually takes a spherical form. Specialized equipment is required to discover strong evidential value in all three elements and confirm if a gun had been fired by a specific suspect(s).

The Electron microscope (EM) is a powerful device that utilizes a beam of negatrons to generate images of specimens under analysis. It enables magnification at much higher levels, allowing the observation of significantly smaller objects. These instruments are large and expensive, requiring substantial expertise and training to operate. In all electron microscopes, the control of negatron pathways is achieved through the application of electromagnetic and electrostatic lenses.

An electromagnetic lens is created by coiling a wire around the outside of a tube through which a current can be passed, generating an electromagnetic field. The negatron beam travels through the center of the wire spiral and down the EM column towards the sample. Electrons are highly responsive to magnetic fields and can be manipulated by adjusting the current flowing through the lenses. Two types of EM exist, namely Transmission Electron Microscope (TEM) and Scanning Electron Microscopy (SEM).

Transmission electron microscopy utilizes a powerful electron

beam generated by a cathode and shaped by magnetic lenses. The electron beam, which has passed through a thin specimen, contains details about its structure. This information is amplified by a series of magnetic lenses and then captured on a photographic plate by striking a fluorescent screen.

SEM is a technique that uses a beam of negatrons to produce exaggerated images of a sample. This is done by observing secondary negatrons emitted from the surface when excited by the primary negatron beam. The surface of the sample is scanned with sensors, and an image is constructed by mapping the detected signals. The impact of the beam on the sample allows for the production of three-dimensional (3D) images at high magnification levels.

SEM has the ability to reveal detailed information about atom surfaces using GSR examples. The large atoms of partially burned powder and analyzed residue areas may appear to come from contaminated materials rather than just the specimen. In SEM, backscattered electrons (BSE) are formed when incoming electrons collide with the nucleus of the target atom, causing electrons to be knocked off.

The use of Backscattered Electron Imaging (BSE) allows for the observation of contrast between countries with different chemical compositions. In these images, heavy metal elements appear brighter, while lighter metal elements appear darker. Scanning Electron Microscopy (SEM) can be combined with Energy Diffusing X-ray Spectrometry (EDS or EDX) to provide information about the elemental composition of the sample being analyzed. Currently, the most successful technique is SEM/EDX, which focuses on the inorganic atoms of Gunshot Residue (GSR). This technique not only allows for the production of the elemental composition of individual atoms but also

enables the generation of images that display the morphology and features of GSR. This is significant because these two techniques provide a unique identification of GSR atoms, which can help in determining the guilt of a suspect in a crime.

Particles can be identified as possibly being GSR or not having fired the arm. This technique has the advantage of being able to analyze individual atoms of GSR, specifically the elements lead, barium, and antimony, which can be easily identified using this method (Jackson et al.).

The EDX technique utilizes a negatron beam to bombard a sample and detect the x-rays emitted, allowing for analysis of the elemental composition. It can analyze characteristics as small as 1 ?m or less. When the SEM's negatron beam strikes the sample, it dislodges electrons from the surface atoms.

The negatrons from the land province are replenished by negatrons from a higher province, which creates a negatron hole. This hole results in the emission of an x-ray to balance the energy discrepancy between the two negatron provinces. An energy diffusing spectrometer can be used to measure both the figure and energy of the x-rays emitted from a specimen. This measurement provides direct information on the energy difference. The information can be interpreted in various forms, including the x-ray spectrum. However, SEM/EDX cannot determine if a person fired a weapon at any point. The disadvantages of using this technique are its high cost.

The machine requires limited handy skills and a significant amount of preparation as it is considered a specialized piece of equipment. The SEM examines specific particulates at high magnification, while the EDX allows elemental analysis of samples. The usage of SEM/EDX

for GSR analysis has increased from 21% to 26%, demonstrating its reliability and accuracy. When presenting evidence in court, positive results obtained through SEM/EDX analysis are rarely challenged by the judge. More than 72% of research labs that analyze GSR use SEM/EDX and over 50% of the stub, which is composed of aluminum and acts as a conducting check, is directly placed into the SEM/EDX machine without any sample pre-treatment (Ronald et al. 1996: 197) to initiate the analysis.

EDX expands the application of SEM by enabling elemental analysis within parts as small as a few micrometers. This method can detect all elements from the periodic table. Other methods such as Time of Flight-Secondary Ion Mass Spectrometry (TOF-SIMS), x-ray micro-fluorescence, and color/spot testing have also been used for identifying both organic and inorganic gunshot residue (GSR), but the specific method chosen varies.

Inductively coupled plasma (ICP), neutron activation analysis (NAA), gas chromatography (GC), and atomic absorption spectrometer (AAS) are commonly used analytical techniques. TOF-SIMS, although having advantages over SEM/EDX, falls short in high-resolution imaging. TOF-SIMS is effective for analyzing smokeless black powders due to its high vacuum conditions, but it is unsuitable for volatile components like nitro-glycerine (NG), which is a liquid substance derived from glycerin.

azotic and sulfuric acid. (Oliver et al. 2010)

Mentions

1. Suzanne Bell (2006). Forensic Chemistry. USA: Pearson Education Inc. 447.
2. Andrew R. W Jackson and Julie M. Jackson (2011). Forensic Science. 3rd erectile dysfunction. London: Pearson Education Inc. 311-317.
3. Ian K.

Pepper (2005). Crime Scene Investigation: Methods and Procedures. 2nd edition. United Kingdom: McGraw-Hill Company.

118. Diaries

Ronald L.

Singer. 1 M. S.

Dusty Davis, 2 B.S., and Max M. Houck.

3 M. A. (1996). Journal of Forensic Science. A Survey of Gunshot Residue Analysis Methods. 41 (2).

195-198.

Analysis of Gunshot Residue and Associated Materials-A Review. Journal of Forensic Sciences. 55 (4).

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