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The advantages of organic gunshot residue compared to inorganic gunshot residue Essay Example

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Gunshot Residue

Gunshot Residue

Introduction

Crime involving the use of firearms is common in the society since the development of the first firearm. Britain happens to be one of the countries with the highest incidences of criminal activities committed using firearms. Although identifying a criminal who has used a firearm used to be a big challenge in the past, the technological advancements that have occurred in the recent past has made it easy for forensic experts to identify the shooter even many hours after the shooting incidence (Singer et al. 1996, p. 197). Although bullet cartridges are still widely relied on, this method is proving less effective because criminals can use firearms and take their time to remove all the bullet cartridges at the shooting site, to remove any evidence that might link them to the shooting (Wolten & Nesbitt 1980, p. 534). However, even as criminals become clever, forensic experts have also gone a notch higher and are currently relying heavily on gunshot residue not only to identify the shooter, but also to link the bullet with the wound caused to the victim by a firearm. Forensic experts use either organic GSR or inorganic GSR for such forensic analysis (Bueno et al. 4334; Taudte et al. 2016, p. 2569). This paper explains the advantages of organic GSR over inorganic GSR in firearm forensic analysis.

Gunshot residue is widely used today in forensic analysis to identify a shooter and link the wound to a particular firearm. GSR is basically the materials that are partially burnt or not burnt when firing using a gun (López-López et al. 2012, p. 3581). Conventionally, when a gunshot is fired, hot gases are generated at high pressure which causes GSR to escape from the firearm opening. GSR can come out from different points during firing, including primer, cartridge casing, propellant or bullet (Romolo & Margot 2001, p. 199).

For analysis purposes, forensic investigators rely on two types of GSR, namely organic and inorganic GSR. Organic GSR is the partially burnt or un-burnt materials or particles that exude from a firearm during firing. The particles come from powders comprising of propellants, such as nitrocellulose, nitro-glycerine, methyl centralite and diphenylamine. These organic particles evaporate during firing before re-condensing. Inorganic GSR, on the other hand, are particles generated from traditional ammunitions and consists of lead, antimony, barium, arsenic, copper, silver, bismuth, titanium and zinc among other compounds (Tarifa & Almirall 2015, p. 171).

Although traditionally inorganic GSR was the most commonly used technique for identifying a shooter, inorganic GSR has many limitations and has proved less reliable in many cases. To address the shortcomings associated with inorganic GSR, forensic investigators presently rely mainly on organic GSR, which is not only more accurate, but also more liable as it allows for field testing to assist in investigation in real time (Romolo & Margot 2001, p. 201). It is important to note that organic GSR contains a variety of chemical compounds key among them being diphenylamine (DPA, a stabilizer), methyl centralite (MC), dimethylphthalate (DMP), 4NDPA, ethyl centralite (EC), and nitrodiphenylamine (National Institute of Justice 2015). The figure below shows the chemical structures of the compounds used in organic GSR.

Chemical structures of Organic GSR Compounds

the advantages of organic gunshot residue compared to inorganic gunshot residue

Source: National Institute of Justice (2015)

The first main advantage of organic GSR in forensic analysis is that the organic particles produced during firing are deposited on various surfaces such as skin where they can be detected on these surfaces several hours after the firing. This is unlike inorganic compounds that disappear from the surfaces after firing, which makes them difficult to detect just few minutes after firing (Moran & Bell 2014, p. 6072). In fact, even as few shots as one or two gunshots produce enough organic GSR that are detectable several hours after firing.

The other advantage of organic GSR is that unlike inorganic GSR that are lost to secondary transfer. It is indicated that, organic GSR are not lost through secondary transfer and can be detected even 12 to 14 hours (Dalby et al., 2010, p. 924). The only two mechanisms of loss for organic GSR are skin permeation and evaporation. Moreover, organic GSR compounds can be gathered by hand several hours after firing, which is impossible with inorganic compounds. Besides, hand swab for organic compounds remain stable for at least 2 weeks when kept at low temperature, which means it can be analyzed many days post-firing, a property that is not present in inorganic GSR, according to the Forensic Technology Center of Excellence (2015).

Conclusion

Organic GSR and inorganic GSR are the common forensic techniques used in addressing criminalities involving the use of firearms. However, as indicated in the discussion, organic GSR has more advantages over inorganic GSR since it can be detected on skin and other surfaces several hours post-firing, not lost through secondary transfer and the fact that organic GSR remains stable for as long as 2 weeks post firing when stored at two temperatures.

References

Bueno, J., Sikirzhytski, V., & Lednev, I. K 2012, “Raman spectroscopic analysis of gunshot residue offering great potential for caliber differentiation,” Anal, Chem., vol. 84, no. 10, pp. 4334–4339

Dalby, O., Butler, D., & Birkett, J. W2010, “Analysis of gunshot residue and associated materials—A review,” Journal of forensic Sciences, vol. 55, no. 4, pp. 924–943.

Forensic Technology Center of Excellence 2015, In-Brief: Organic Gunshot Residue Analysis for Potential Shooter Determination. U.S. Department of Justice, National Institute of Justice, Office of Investigative and Forensic Sciences.

López-López, M., Delgado, J. J., & García-Ruiz, C 2012, “Ammunition identification by means of the organic analysis of gunshot residues using Raman spectroscopy,” Anal Chem., vol. 17, no. 8, pp. 3581-5. Doi: 10.1021/ac203237w.

Moran, J. W., & Bell, S 2014, “Skin Permeation of Organic Gunshot Residue: Implications for Sampling and Analysis,” Anal. Chem., vol. 86, no. 12, pp 6071–6079. DOI: 10.1021/ac501227e

National Institute of Justice 2015, Organic gunshot residue analysis for potential shooter determination, viewed 17 November 2016 http://www.crime-scene-investigator.net/organic-gunshot-residue-analysis-for-potential-shooter-determination.html

Romolo, F. S., & Margot, P 2001, “Identification of gunshot residue: a critical review,” Forensic Sci. Int., vol. 119, no. 2, pp. 195–211

Singer, R. L., Davis, D., & Houck, M. M 1996, “A survey of gunshot residue analysis methods,” J. Forensic Sci., vol. 41, no. 2, pp. 195–198

Tarifa, A., & Almirall, J. R 2015, “Fast detection and characterization of organic and inorganic gunshot residues on the hands of suspects by CMV-GC-MS and LIBS,” Sci Justice. Vol. 55, no. 3, p. 168-75. doi: 10.1016/j.scijus.2015.02.003.

Taudte, R. V., Roux, C., Blanes, L., Horder, M, Kirkbride, K. P. & Beavis, A. 2016. ‘The development and comparison of collection techniques for inorganic and organic gunshot residues,” Analytical and Bioanalytical Chemistry, vol. 408, no. 10, pp 2567–2576

Wolten, G. M., & Nesbitt, R. S 1980, “On the mechanism of gunshot residue particle formation,” J. Forensic Sci., vol. 25, no. 3, pp. 533–545.