Possibilities of Fort "12R" and "AE 790G1" pistols identification using step-by-step discriminant analysis

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National Pirogov memorial medical university

BSMU

Possibilities of «Fort 12R» and «AE 790G1» pistols identification using step-by-step discriminant analysis

Kusliy Yuriy Yuriyovych,

postgraduate of the department forensic medicine and law

Hel Andrey Pavlovich,

associate professor of the department forensic medicine and law

Vanchulyak Oleg Yaroslavovych,

professor of the department of forensic medicine and medical jurisprudence,

Vinnytsya

Abstract

Identification of the instrument of crime is one of the key issues faced by experts. Examinations related to the use of firearms are particularly difficult, where, in addition to this, the issue is establishing the distance of the shot. For the most part, in developed countries, the solution to these issues is achieved through the use of controlled shots with subsequent analysis of the residual components of the shot. However, in addition to them, there are other physical evidences worth paying attention to, such as the specifics of clothing damage, morphological characteristics of body damage, which should also be taken into account. The purpose of the study was to create models using step-by-step discriminant analysis for the identification of «Fort 12R» and «AE 790G1» pistols based on the features of the deposition of the gunshot residue and the features of damage to non-biological simulators of the human body and clothing. In order to achieve the goal, 120 gelatin blocks were made that imitated the soft tissues of the human body and were then covered with one of the types of clothing (cotton fabric, denim or leatherette) or left bare. Shots were fired from «Fort 12R» and «AE 790G1» pistols in the conditions of a shooting range at close range, 25 and 50 cm with further analysis of damage to the block and clothing, laboratory determination of the residual components of the shot and calculations of the parameters of the temporary cavity. The obtained results were analyzed in the statistical package «Statistica 6.0». Taking into account the specifics of damage to a non-biological human body impersonator and its covering elements in the form of clothing, data on the deposition of the residual components of a shot, reliable discriminant models were built that were correct in 77.5% of cases for identifying a gun and in 99.2% of cases for identifying the distance of a shot. The obtained results will facilitate the work of institutions that directly participate in the examination of gunshot injuries, in particular the bureau of forensic medical examination and scientific research expert forensic centers under the Ministry of Internal Affairs of Ukraine.

Keywords: discriminant analysis, non-lethal weapons, gunshot residue, firearm, gunshot injury.

Анотація

Куслій Юрій Юрійович аспірант кафедри судової медицини та права, Вінницький національний медичний університет ім. М. І. Пирогова

Гель Андрій Павлович доцент кафедри судової медицини та права, Вінницький національний медичний університет ім. М. І. Пирогова

Ванчуляк Олег Ярославович професор кафедри судової медицини та медичного правознавства, БДМУ

Можливості ідентифікації пістолетів «Форт 12Р» та «AE 790G1» за допомогою покрокового дискримінантного аналізу

Ідентифікація знаряддя злочину є одним з ключових питань, з яким стикаються експерти. Особливу складність мають експертизи, що стосуються застосування вогнепальної зброї, де окрім цього частин питанням є встановлення дистанції пострілу. Здебільшого в розвинених країнах вирішення даних питань досягається за рахунок використання контрольованих пострілів з послідуючим аналізом залишкових компонентів пострілу. Проте, окрім них вартими уваги є і інші речові докази, як то особливості пошкодження одягу, морфологічні характеристики ушкодження тіла, які також варто приймати до уваги. Метою дослідження було створення моделей з допомогою покрокового дискримінантного аналізу для ідентифікації пістолетів «Форт 12Р» і «AE 790G1» базуючись на особливостях відкладання залишкових компонентів пострілу та особливостей пошкоджень небіологічних імітаторів тіла людини та одягу. Для досягнення поставленої мети виготовлено 120 желатинових блоків, що імітували м'які тканини тіла людини і в подальшому покривали одним з видів одягу (бавовняна тканина, джинсова тканина чи шкірозамінник) або лишали голими. Постріли виконували з пістолетів «Форт 12Р» і «AE 790G1» в умовах тиру з дистанцій впритул, 25 та 50 см з подальшим аналізом пошкоджень блоку та одягу, лабораторним визначенням залишкових компонентів пострілу та розрахунками параметрів тимчасової порожнини. Отримані результати аналізували в статистичному пакеті «Statistica 6.0». Враховуючі особливості пошкоджень небіологічного імітатору тіла людини та його покривних елементів у вигляді одягу, дані щодо відкладання залишкових компонентів пострілу побудовані достовірні дискримінантні моделі, коректні в 77,5% випадків для ідентифікації пістолету та в 99,2% випадків для ідентифікації дистанції пострілу. Отримані результати дозволять полегшити роботу установ, що безпосередньо приймають участь в експертизі вогнепальної травми, зокрема бюро судово - медичної експертизи та науково-дослідні експертні криміналістичні центри при МВС України.

Ключові слова: дискримінантний аналіз, нелетальна зброя, залишкові компоненти пострілу, вогнепальна зброя, вогнепальна травма.

Main part

Statement of the problem. The problem of the spread of firearms in the world has taken on a threatening form - the number of injuries and deaths as a result of their use is increasing. In Sialkot (Pakistan) from 2008 to 2012, 1,240 cases of injury were recorded, of which 880 were caused by homemade weapons. In 52.2% of cases, the cause of injury was domestic conflicts, in 19.3% robbery, 9.6% accident, 6.1% self-harm, and 6.1% - use by law enforcement agencies [1]. In Colorado (USA) from 2008 to 2018, 308 cases of the use of firearms against children under the age of 18 were recorded. Of these, 34 cases resulted in death. The average age of the victims was 14 years [2].

Taking into account such challenges today, forensic medicine and related specialties are interested in the most scientifically based research that will allow accurate answers to police questions. One of these ways is the use of modern laboratory research methods, such as X-ray fluorescence spectroscopic analysis [3], etc. However, it is equally important to use all available material evidence.

In order to identify such potentially important material evidence, it is most expedient to use controlled shooting with the use of optically transparent substances that mimic human body tissues as much as possible [4]. Further application of powerful statistical processing methods will allow to highlight key parameters that are important for weapon identification and shot distance.

Connection of the publication with planned scientific research works. The work was carried out as part of the research work of the National Pirogov Memorial Medical University, Vinnytsya at the expense of state funding of the Ministry of Health of Ukraine: «Characteristics of damage to human body tissue simulators caused by non-lethal weapons» (state registration number 0121U107924).

The purpose of the article - based on the data on the deposition of the gunshot residueand the features of damage to a non-biological simulator of the human body and various types of clothing, build models using step-by-step discriminant analysis for the identification of «Fort 12R» and «AE 790G1» pistols.

Research objects and methods. To achieve the goal, the authors used a 10% solution of food gelatin type A 270 Bloom (TM «Junca Gelatines SL», Spain), from which standardized gelatin blocks [5] were made in the amount of 120 units. On the basis of the shooting range of the Vinnytsia Scientific Research Expert Forensic Center of the Ministry of Internal Affairs of Ukraine, shots were fired at the blocks using non-lethal pistols «Fort 12R» and «AE 790G1». Previously, the blocks were divided into 4 groups depending on the type of coating: bare blocks, blocks covered with cotton fabric, denim fabric. Microscopic examination was carried out using a MBS-10 microscope under magnification from *4.8 to *56.

To detect gunshot residue, the following were used: the chromato-mass spectrometric method on the Shimadzu GC-2010 Plus device and infrared microscopy on the Fourier-transform infrared spectroscopy Nicolet iN10 of the company «Thermo Fisher Scientific» (detection of the components of nitrocellulose gunpowder, namely, diphenylamine and centralites); X-ray fluorescence spectroscopy using the ElvaX Plus device (detection of qualitative and quantitative characteristics of overlapping elements).

The following methods were used to estimate the parameters of the temporary cavity formed when a shot was fired into a non-biological simulator of the human body: according to Fackler and Malinowski [5], Ragsdale and Josselson [6] and Schyma [7], which corresponded to the following values - The total crack length method (TCLM,) The Fackler's wound profile method (FWPM) and The polygonprocedure method (PPM), respectively.

Committee on Bioethics of National Pirogov Memorial Medical University, Vinnytsya (protocol №11 From 03.12.2020) found that the studies do not contradict the basic bioethical standards of the Declaration of Helsinki, the Council of Europe Convention on Human Rights and Biomedicine (1977), the relevant WHO regulations and laws of Ukraine.

Statistical processing of the obtained results was carried out in the licensed statistical package «Statistica 6.0» using step-by-step discriminant analysis.

Research results and their discussion. Taking into account the features of damage formation of the «clothing + non-biological human body simulator» complex and individual non-biological human body simulators, as well as trace-forming elements of the structures of the «Fort 12R» and «AE 790G1» pistols when fired from these pistols at close range, 25 cm and 50 cm the discriminant function covers 83.3% of the parameters characteristic of the Fort 12R pistol and 71.7% of the parameters characteristic of the AE 790G1 pistol. In general, the model is correct in 77.5% of cases.

Among the parameters characteristic of the Fort 12R and AE 790G1 pistols, the discriminant variables are the specific sum of the crack lengths in the FWPM body simulator at a depth of 2 cm (FWPM2), the shot distance (VPOS), the defect area (SD), the non-biological human body simulator without or with the presence of matching (cotton, denim, or leather) clothing (TKAN), presence or absence of centrality (NC), presence or absence of diphenylamine (ND), specific sum of crack length in PPM body simulator at 1 cm depth (PPM1) and presence or absence of soot (K) (Table 1). Among these parameters, the distance of the shot and the area of the defect have the greatest contribution to the discrimination between the pistols. The set of all variables has a slight reliable discrimination (Wilks' Lambda=0.535; p<0.001) between the indicators characteristic of the «Fort 12R» and «AE 790G1» pistols (see Table 1).

For each of the groups, we determined the classification indicator (Df), by means of which the indicators of the formation of damage and trace-forming elements shown in Table 1 can be classified as «typical» for «Fort 12R» or «AE 790G1» pistols. Below, in the form of equations, the definition of the classification indicator is given, where assignment to the «Fort 12P» pistol is possible with a Df value close to 160.5; for the «AE 790G1» gun - with a Df value close to 184.5:

Df (pistol «Fort 12R») = - FWPM2x0,255 + VPOSx77,78 + SDx 16,93 - TKANx0,493 + NCx6,327 - NDx14,79 + PPM1x1,382 + Kx69,07 - 160,5;

Df (pistol «AE 790G1») = - FWPM2x0,080 + VPOSx83,45 + SDx20,57 + TKANx0,042 + NCx8,950 - NDx21,29 + PPM1x1,471 + Kx72,29 - 184,5; where (here and in the following), the specific sum of the length of the FWPM cracks in the body simulator is in mm; the distance of contact shot - 1, from a distance of 25 cm - 2, from a distance of 50 cm - 3; defect area - in cm2; bare block without fabric - 1, with cotton - 2, with jeans - 3, with leather substitute - 4; presence - 2 or absence - 1 centrolite; presence - 2 or absence - 1 of diphenylamine; the specific sum of the length of the PPM cracks in the body simulator - in mm; presence - 2 or absence - 1 of soot.

Table 1. Report of the discriminant analysis of the identification of guns «Fort 12R» or «AE 790G1» depending on the characteristics of indicators of damage formation and trace-forming elements