Chemical criminalistics

Forensic Chemistry (Chemical Criminalistics). This branch of science relates to the application of chemical knowledge and techniques to die study of physical evidence connected with crime. Investigation of firearms, ammunition and expls is one of the duties of a forensic chemist Refs i) A. Lucas, "Forensic Chemistry and Scientific Criminal Investigation 1, Longmans, Green, London (1935), Chap 7, Explosives Chap 11, Fireworks 2) H. 

A. Maehly, and L. Stromberg, Chemical Criminalistics (New York Springer-Verlag, 1981), 189. 

Figure 16.2. Schematic presentation of procedure for identification of chemical compounds and other traces for forensic toxicology or criminalistic purposes [4],...

A common criminalistics problem to which materials science technology is applicable is the recovery of serial numbers which have been obliterated from metal items. We discuss here the metallurgical background of serial number obliteration and recovery, the theory and practice of chemical or electro-chemical methods which form the bulk of the presently employed methods, some techniques based on alternate approaches that are mostly experimental or have been proposed and, lastly, a recently developed serial number marking technique capable of producing more permanent markings. 

Traces are identified by determining their chemical composition and certain physicochemical properties, and comparison with reference material (database) or comparative material collected from the suspect. Criminalistic laboratories create extensive databases on the physical features and production of glass, paints, papers, fabrics and other materials, as well as collecting thousands of samples for comparison purposes. 

To identify materials forming a criminalistic trace, it is necessary to study their morphology, determine their chemical composition (mainly qualitative) and study some physico-chemical properties. Because the sample of material forming the trace is small, microanalytical methods are applied for identification. Methods that... 

Microspectrometry is an indispensable technique in criminalistic analyses, being a combination of optical microscopy and spectrometry. Microscopy creates, records and interprets magnified images, whereas spectrometry uses emission, absorption and reflection of radiant energy by matter to determine its structure, properties and composition. On the basis of the type of energy applied, microspectrometry can be divided into IR, visual and ultraviolet (UV-vis), and Raman microspectrometry. This group also includes X-ray microspectrometry, in which an electron microscope takes the place of an optical microscope. Infrared and Raman microspectrometry enable determination and comparison of the chemical composition of studied samples UV-vis microspectrometry serves to compare the colour of samples in an objective way that is independent of the observer and X-ray microspectrometry allows determination of the elemental composition. 

The obtained analytical data allow a conclusion to be drawn about whether the compared paint samples could have originated from the same coat of paint or not. If the reference material (i.e. from the suspect) is not available, only establishment of the kind of paint and the type of paint coat is possible. In the case of automobile paints, it is also possible to find the model of car involved in an accident. Eor this purpose, analytical data are compared with a database containing information about the type of paint coatings (layering, chemical composition of each layer) used in various types and models of vehicles in Europe. Such a collection has existed in Europe since 1995 and is updated every year with information on new products. Experts from many criminalistic laboratories have participated in its creation. Comparison with such a database provides information about the make and model of the vehicle involved in the incident and its year of production. It is thus helpful in identifying the perpetrator s vehicle. It should be emphasised that identifying the make and year of production of a vehicle on the basis of a paint database only applies to vehicles with a factory-new coat of paint. 

Criminalistics Refers to the analysis of pattern, chemical, and biological evidence often used interchangeably with forensic science. 

Saferstein, Richard. Criminalistics An Introduction to Forensic Science. 10th ed. Upper Saddle River, N.J. Prentice Hall, 2011. Provides an introduction to forensic science, detailing the techniques to analyze physical, biological, and chemical evidence. 

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