The development of science and technology undoubtedly gives positive results in the disclosure and investigation of crimes. The importance of the use of material evidence in criminal proceedings and expert opinions as the most important objective sources for the creation of a reliable evidentiary base is steadily increasing. The need for the qualified, effective and timely use of forensic tools and methods today is an integral part of the investigation of murders, rapes, robberies, thefts, crimes related to drug trafficking and other crimes.
The Concept of Forensic Science
Forensic science is a kind of process of objective reality cognition carried out by applying the methods of various sciences. The study of the physical evidence is similar to scientific research; it differs by some features inherent in a practical activity that is scientifically based in the field of forensic science, using the provisions of some sciences, including legal, natural, technical and humanitarian ones. These provisions, scientific methods, and means are used in the work of forensic experts and expert institutions for solving practical problems of establishing the truth in the civil or criminal case or the case of an administrative offense (Strom & Hickman, 2014).
The methods of forensic expert practice are based on appropriate scientific methods, depend on the nature and properties of the object of research and are based on the experience of solving specific expert tasks, including algorithmic rules and those developed by the expert himself (Rivers & Dahlem, 2013).
Special Methods of Physical Evidence Analysis
In expert and preliminary studies of physical evidence, in addition to general scientific methods, special methods are also used. Special methods are based on the principle of generality and can, in turn, be divided into general expert used in most classes of forensic examinations and studies and private expert, used only in the given particular type (form) of judicial expertise and research. The system of general expert methods of investigating material evidence includes methods of image analysis; methods of morphological analysis; methods of composition analysis; methods for analyzing the structure; methods for studying physical, chemical and other properties.
Methods of image analysis are used to study traditional forensic objects – human traces, guns and tools, vehicles, as well as documents, etc. By morphology, the external structure of the object is meant, as well as the shape, dimensions and mutual arrangement of its constituent structural elements on the surface and in the volume arising under investigation. The most common methods of morphological analysis are the methods of optical microscopy – a set of methods of observation and research using an optical microscope, namely, ultraviolet and infrared microscopy, stereoscopic microscopy, comparative microscopes, transmission electron microscopy, scanning electron microscopy.
Element analysis methods are used to establish element composition, namely, the qualitative or quantitative content analysis of certain chemical elements in a given substance or material. Their range is quite wide, but the most common in expert practice are the following: emission spectral analysis, laser micron spectral analysis, X-ray spectral analysis.
The molecular composition of an object is understood as the qualitative (quantitative) content of simple and complex chemical substances in it, for the establishment of which molecular analysis methods are used. They are chemical analytical methods and micro crystalloscopy. Although, the main methods for studying the molecular composition of physical evidence at present are molecular spectroscopy and chromatography.
Metallographic and X-ray analysis are used to study the crystal structure of objects. With the help of metallographic analysis, changes in the macro- and microstructure of metals and alloys are studied in connection with changes in their chemical composition and processing conditions. X-ray diffraction analysis makes it possible to determine the orientation and dimensions of the crystals, the source of origin, or other details, to determine the causes of fire, explosion or road accident by destructions.
Qualitative and Quantitative Analysis of Physical Evidence
An integral part of forensic science is analytic chemistry. The main task of analytical chemistry is to determine the qualitative and quantitative composition of the substance and to identify whether a matter is organic or inorganic. The qualitative analysis consists of determining the chemical elemental composition of the substance, what chemical elements (or groups of elements) are exactly included (Bowen, 2016).
In forensic science, identification is the establishment of a substance (object) by a combination of general and particular characteristics. The quantitative analysis consists of determining the quantitative content of chemical elements or their groups in the analyzed substance. The tasks are solved by a method of influencing a substance with the subsequent registration of physicochemical or physical properties of a substance, which makes it possible to carry out qualitative, quantitative analysis, and to establish the structure of a substance or conduct its identification.
In the analysis of physical evidence, organic substances that are of biological origin and substances of inorganic origin are considered. As evidence of organic origin traces of blood, saliva, sweat, etc. are considered. Left at the crime scene substances of inorganic origin includes dust, paint, fibers, etc. To identifying physical evidence to ensure that accurate and reliable scientific results are obtained forensic scientist uses a combination of image analysis methods with chemical analytical methods and micro crystalloscopy. Forensic scientist defends his or her scientific conclusions and opinions in a court of law by providing evidence received legally and listed as case evidence. The forensic tools and methods are the basic of the crime investigations and the evidence base analysis that can be used by the prosecution.
References
Bowen, R. T. (2016). Ethics and the practice of forensic science. Boca Raton, Florida: CRC Press.
Rivers, D. B., & Dahlem, G. A. (2013). The science of forensic entomology. New York, USA: John Wiley & Sons.
Strom, K. J., & Hickman, M. J. (Eds.). (2014). Forensic science and the administration of justice: Critical issues and directions. Thousand Oaks, California: Sage Publications.