Gunshot residue techniques

A Del Electronics, Model ESP-100A, electrostatic precipitator was used for sample collection. Cigarette smoke particles were found to give approx the same particle distribution pattern on the collection filter paper as the gunshot residue, and since the smoke stains the paper, this provided a v rapid technique for optimizing operation conditions. With a flow rate of 15cfm and a corona current of 125 uA, the residue collects primarily on a narrow band across the sample paper. Samples were collected on Whatman No 1541 filter paper which lined the inside of the sample collection tube. The presence of this paper allowed air to flow only thru the center of the tube, so particle collection was made upon the filter paper exclusively. The filter paper samples were pelletized prior to neutron activation analysis... 

It should be noted that a comparable survey and assessment task in the gunshot residue detection area recently has been completed by Aerospace. The long-range objectives of this research program are to develop rapid, reliable and inexpensive techniques and equipment for use by crime laboratories in the detection of gunshot residues on the hands of suspects. 

I shall describe the useful properties of photoluminescence and the current application of these properties in forensic science. New applications of photoluminescence developed or being investigated in our laboratory are also described. We have used photoluminescence techniques to (a) locate and identify seminal stains, (b) detect lead and antimony gunshot residue at the nanogram level, and (c) discriminate between different glass and human (head) hair samples. All of these techniques can be carried out rapidly in the crime laboratory. 

I describe here the results of our preliminary study (22) of the application of photoluminescence techniques to gunshot residue detection. The key objective in this study was to develop a rapid, reliable, and convenient method of detection for use in the crime laboratory on the basis of the detection of lead, antimony, and barium. We did not attempt to repeat the extensive work already carried out with neutron activation analysis concerning the importance of the detection of these elements and the interpretation of findings. The literature concerning photoluminescence was surveyed for methods of analysis for antimony, barium, and lead that would be (a) reliable, sensitive, and quantitative ... 

M. D. Cole, N. Ross, and J. W. Thorpe, Gunshot Residue and Bullet Wipe Detection Using a Single Lift Technique, AFTE Journal 24, no. 3 (July 1992) 254. 

A. Zeichner, H. A. Foner, M. Dvorachek, P. Bergman, and N. Levin, Concentration Techniques for the Detection of Gunshot Residues by Scanning Electron Microscopy/Energy Dispersive X-Ray Analysis (SEM/EDX), Journal of Forensic Sciences 34, no. 2 (March 1989) 312. 

This chapter introduced the application of HPLC and HPCE to forensics, the use of science in the judicial process. We explored how these separation techniques are used in testing for illicit drugs, gunshot residues and explosive constituents, pen inks, modified proteins, and nucleic acids. 

Firing tests conducted with larger than 0.22 cal ammo showed that even greater sensitivity for detection of Ba and Sb in airborne gunshot residues can be obtained using these NAA techniques ... 

Amperometric techniques are very useful for detecting analytes that have been separated by chromatographic means but have no chromophores or other easy means of detection. Adsorptive stripping voltammetry (ASV) can be used for the direct sensitive analysis of metals in many types of sample matrix. For example, ASV has been used to determine cadmium, lead and zinc in urine, copper and bismuth in human hair tin in fruit juice, zinc and copper in fish and lead in gunshot residue. Stripping analysis can also be used for other applications such as determining flavanols in wine °, inorganic compounds such as cyanide and pharmaceuticals. ... 

Scanning electron microscopy with energy dispersive X-ray spectrometry has found extensive applications in the analysis of glass, paint, fibers, and especially in the identification of gunshot residues (where it is the method of choice). This technique offers high resolution, great depth of field, and qualitative and quantitative information on small samples. However, although this technique has much to offer, its use in crime detection is often overrated. 

See also-. Extraction Supercritical Fluid Extraction. Forensic Sciences Gunshot Residues Thin-Layer Chromatography. Fourier Transform Techniques. Gas Chromatography Mass Spectrometry Forensic Applications. Microscopy Appiications Forensic. X-Ray Absorption and Diffraction X-Ray Absorption X-Ray Diffraction - Powder. 

Pyrolysis GC (Py-GC) has been used for the identification and comparison of propellants. Smokeless powder propellants were analyzed by pyrolysis capillary GC-MS, and main organic propellant constituents together with additives could be detected and used as criteria for comparison. However, the standard technique for the examination of gunshot residues is scanning electron microscopy. 

See also Forensic Sciences Gunshot Residues Hair. Microscopy Applications Environmental. Microscopy Techniques Electron Microscopy Specimen Preparation for Electron Microscopy. X-Ray Fluorescence and Emission Energy Dispersive X-Ray Fluorescence. 

Analysis starts with qualitative presumptive tests that narrow down the list of potential analytes and directs subsequent analysis. P resumptive tests belong to a family of analytical techniques referred to as wet chemical methods. Most are based on observing results when specific reagents are added to small portions of the samples. Color and crystal tests, as they are commonly called, are used in analyzing drugs, gunshot residues, and explosives. These tests will be discussed in detail in subsequent chapters. 

A review of many types of instrumental analysis used for the characterization of gunshot residues has appeared recently. This includes descriptions of the use of atomic absorption spectroscopy, neutron activation analysis and X-ray fluorescence as well as various mass spectrometry techniques after preconcentration of analytes using separation methods such as HPLC and capillary electrophoresis. In addition, atomic absorption spectroscopy has been used to characterize the brass used in different production lots of cartridge cases. 

Probably no branch of science is held to higher scmtirty than forensics. In a forensics laboratory, when trace evidence is often all there is available from a crime scene, a trained microscopist is imperative. Dmg tests, blood tests, gunshot residue, glass matching, and fiber and hair analysis are all performed on trace evidence using a variety of microchemical techniques, most often with a polarized light microscope. 

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