Comparison of temporal cavity indicators when firing "FORT 12R" and "AE 790G1" into a non-biological body simulator

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Introduction
Gunshot injury is a common type of injury that often leads to death. The larger the caliber of the weapon, the greater the chance of a fatal outcome [2]. An analysis of the use of firearms in the city of Benin (Nigeria) from 1998 to 2002 showed 210 cases of fatal use of firearms. Most of them (88.1 %) were committed by criminals and a small part (9.0 %) by law enforcement agencies. 88.5 % of lethal use of weapons was murder, 4.3 % accidental and 0.5 % suicide [1]. Data from the National Electronic Injury Surveillance System in the USA showed that the death rate from the use of firearms is a fairly stable indicator and was 22 % in both 2003 and 2012 [5].
In Ukraine, the urgency of gunshot injury research has increased significantly since 2014 [15]. One of the peculiarities of this issue for Ukraine is the extreme urgency of studying gunshot injuries caused by non-lethal weapons, which are more widespread among different strata of the population, which is related to the peculiarity of the legal system.
One of the key tasks of ballistics is the study of projectile handling on the way to the target. We are talking about both pre-wound ballistics -how the projectile behaves when it comes into contact with the body, the impact of obstacles, weather factors, etc., and wound ballistics -the behavior of the projectile in the object it hit, and first of all -the human body. In wound ballistics, a key place is occupied by the study of temporary cavities, formations that are the result of the transfer of excessive kinetic energy from the projectile to the surrounding tissues and fluids of the human body [4,14].
One of the most effective and expedient methods of studying the temporal cavity is conducting ballistic experiments using a non-biological imitator of the human body, namely gelatin [3]. Due to the transparency and imitation of the physical characteristics of muscle and fat tissue, this material has become the most common. Also common practice is the use of time-lapse cameras, which allows recording processes lasting a fraction of a second [18] or combining gelatin with biological imitators of the human body [12]. At the same time, there are still ongoing discussions about the influence of various variables on the characteristics of gelatin, such as temperature factors, preparing features, etc. [13].
Taking into account the need to study the features of the temporary cavity for modern models of non-lethal firearms (primarily common in Ukraine), there is a need to conduct an experimental study on gelatin samples, taking into account the presence of obstacles in the form of clothing.
The purpose of the work is to conduct a comparative analysis of the indicators of the temporal cavity during shots from "FORT 12R" and "AE 790G1" pistols from different shooting distances into non-biological simulators of the human body covered and uncovered by various types of clothing.

Materials and methods
The study was performed on 120 gelatin blocks made according to the method of Fackler and Malinowski [6], divided into 2 groups of 60 blocks. Group 1 was subject to shooting using the "FORT 12R" pistol, group 2 -"AE 790G1" (both equipped with 9 mm cartridges, elastic bullets of traumatic effect). In each group, 4 subgroups of 15 blocks were formed: 1st group -bare blocks (BB), 2nd groupblocks covered with cotton fabric (CF), 3rd group -blocks covered with denim fabric (DF), 4th group -blocks covered with leatherette (LB). Shootings were carried out from contact range, 25 and 50 cm. After shooting, the blocks were examined according to The total crack length method [6], The Fackler's wound profile method [16] and The polygon-procedure method [17]. The results were photographed in accordance with the rules of forensic photography using an Alpha A6000 Sony digital camera.
The work was carried out as part of the research work of the National Pirogov Memorial Medical University, Vinnytsia 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).
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.
The statistical analysis of the obtained results was carried out in the licensed statistical package "Statistica 6.0" using non-parametric estimation methods. The reliability of the difference in values between independent quantitative values was determined using the Mann-Whitney U-test, and between qualitative values -according to the Weber E.

Results
TCLM values when fired from the "FORT 12R" and "AE 790G1" pistols have the following features: at a cut depth of 1 cm when fired at contact range from the "FORT 12R" pistol, significantly higher values (p<0.  13 and 76.36±17.24, respectively); when shooting from a distance of 25 cm from the "FORT 12R" pistol, significantly lower values (p<0.05-0.01) of the indicator were found when shooting at BB, LB and CF and DF (0, 0, 5.060±3.159 and 5.340±3.727 in accordance); when comparing the values of the indicator when shooting with "FORT 12R" from different distances, significantly higher values (p<0.01) of the indicator were found when shooting at close range, compared to the shooting distance of 25 cm, 50 cm when shooting at BB and LB (25.34±7.69, 0, 0.560±1.252 and 52.70±10.32, 0,0 respectively) and significantly higher values (p<0.05-0.01) of the indicator when shooting at close range, compared to a shot distance of 25 cm, 50 cm and when comparing indicators at shot distances of 25 and 50 cm for both CF and DF (88.28±15.13, 5.060±3.159, 0.860±1.923 and 76.36±17.24, 5.340±3.727 and 0, 0 respectively); when contact shots from the "AE 790G1" pistol revealed significantly lower values (p<0.05-0.01) of the indicator when shooting at BB compared to CF or DF (63.50±15.12, 105.0±24.8 and 106.1±16.1, respectively); when comparing the values of the indicator when shooting from the "AE 790G1" from different distances, significantly higher values (p<0.01) of the indicator were found when shooting at close range, compared to the shooting distance of 25 cm, 50 cm when shooting at all groups of blocks (63.50±15.12, 0, 0 and pistols "FORT 12R" and "AE 790G1" significantly higher (p<0.05-0.01), its values were found when fired from "AE 790G1" when fired at close range in BB and DF or LB (63.50±15. 12 16, respectively); when comparing the values of the indicator when fired from the "AE 790G1" from different distances, significantly higher values (p<0.05-0.01) of the indicator were found when fired at close range, compared to a shot distance of 25 cm, 50 cm when fired at all groups of blocks (19.58±15.00, 0, 0 and 60.48±10.73, 0, 0 and 63.14±24.44, 0, 0 and 59.48±13.16, 0, 0, respectively); when comparing the values of the indicator when fired from "FORT 12R" and "AE 790G1" pistols, significantly higher (p<0.05-0.01) its values were found when fired from "AE 790G1" when fired at close range in BB and LB (19.58±15.00 and 0, 59.48±13.16 and 28.40±6.97, respectively); at a cut depth of 5 cm when contact shots from the "FORT 12R" pistol revealed significantly lower values (p<0.01) of the indicator when shooting at BB or LB compared to CF or DF (0, 0, 24.26±10.75 and 40.16±15.03, respectively); when comparing the values of the indicator when shooting with "FORT 12R" from different distances, significantly higher values (p<0.01) of the indicator were found when shooting at close range, compared to the shooting distance of 25 cm, 50 cm when shooting at CF or DF (24.26±10.75, 0, 0 and 40.16±15.03, 0, 0, respectively); when contact shots from the "AE 790G1" pistol revealed significantly higher values (p<0.05-0.01) of the indicator when shooting in CF compared to BB and DF or LB (37.80±6.97, 0, 12.58 ±12.39 and 18.78±17.41, respectively); when comparing the values of the indicator when shooting from "AE 790G1" from different distances, significantly higher values (p<0.01) of the indicator were found when shooting at close range, compared to the shooting distance of 25 cm, 50 cm when shooting at CF (37.80±6.97, 0 and 0 respectively); when comparing the values of the indicator when fired from "FORT 12R" and "AE 790G1" pistols, its values were significantly higher (p<0.05) when fired at close range from "FORT 12R" in DF (40.16±15.03 and 12.58±12.39, respectively).
The FWPM values when fired from the "FORT 12R" and "AE 790G1" pistols have the following features: at a cut depth of 1 cm when fired at contact range from the "FORT 12R" pistol, significantly lower values (p<0.05) of the indicator were found when fired at LB compared to with BB and CF (11.60±1.78, 14  PPM values when fired from "FORT 12R" and "AE 790G1" pistols have the following features: at a cut depth of 1 cm when fired at contact range from a "FORT 12R" pistol, significantly lower values (p<0.05) of the indicator were found when fired at DF compared to with LB (64.76±6.98 and 71.98±6.73, respectively); when shooting from a distance of 25 cm from the "FORT 12R" pistol, significantly higher values (p<0.01) of the indicator were found when shooting BBs compared to blocks covered with fabrics (53.20±6.37, 20.92±4.46, 28.68±6.11 and 27.72±10.01, respectively); when shooting from a distance of 50 cm from the "FORT 12R" pistol, significantly higher values (p<0.05) of the indicator were found when shooting at DF compared to BB and CF (21.44±5.57, 7.380±4.601 and 7.600±4.710, respectively ); when comparing the values of the indicator when shooting from "FORT 12R" from different distances, significantly higher values (p<0.01) of the indicator were found when shooting at close range, at a cut depth of 2 cm when contact shots from the "FORT 12R" pistol revealed significantly lower values (p<0.05-0.01) of the index when shooting BBs compared to blocks covered with fabrics (67.38±7.23, 77.14±3.73, 81.08±8.86 and 82.70±5.62, respectively), CF compared to LB (77.14±3.73 and 82.70±5.62, respectively); when fired from a distance of 25 cm from the "FORT 12R" pistol, significantly lower values (p<0.05) of the indicator were found when fired at CF compared to LB (15.16±7.39 and 27.32±9.28, respectively); when shooting from a distance of 50 cm from the "FORT 12R" pistol, significantly higher values (p<0.05-0.01) of the indicator were found when shooting at DF compared to BB and LB (11.92±6.26, 3.360±1.704 and 1.900±3.087, respectively); when comparing the values of the indicator when shooting from "FORT 12R" from different distances, significantly higher values (p<0.05-0.01) of the indicator were found when shooting at close range, compared to the shooting distance of 25 cm, 50 cm, and when comparing the indicators at shooting distances 25 and 50 cm in BB  from the "AE 790G1" pistol revealed significantly lower values (p<0.01) of the indicator when shooting BBs compared to CF (0 and 42.58±19.78, respectively); when comparing the values of the indicator when shooting from the "AE 790G1" from different distances, significantly higher values (p<0.01) of the indicator were found when shooting at close range, compared to the shooting distance of 25 cm, 50 cm for CF (42.58±19.78, 0 and 0 respectively); when comparing the values of the indicator when fired from the "FORT 12R" and "AE 790G1" pistols, its values were significantly higher (p<0.05) when fired at close range from the "FORT 12" in DF (49.56±19.01 and 17.06±18.04, respectively).
Since the cut depth of 6 cm was reached only by ammunition when fired at contact range with "FORT 12R" in DF, it was not possible to conduct any comparative analysis for TCLM, FWPM and PPM indicators.

Discussion
The results obtained by us agree quite well with the conclusions of the previous work, which also noted mainly higher damage values when fired from the "AE 790G1" pistol compared to the "FORT 12R" [9].
At the same time, the difference in the indicators of the temporary cavity when firing from "FORT 12R" draws attention. In contrast to the data of our research, the team of authors led by V. Gunas [7] established that "FORT 12R" forms an amphora-like profile of the temporary cavity, which is more reminiscent of the data obtained when fired with "AE 790G1". The explanation of this phenomenon can be both the design features of the "FORT 12RM" or the cartridges for it (this gun is produced with specific 45 Rubber bullets), and the features of the experimental model performed in the study (instead of blocks, shots were fired into torso simulators).
V. V. Shcherbak [20,21] in his publications investigated the parameters of the temporary cavity formed during the firing of the combat pistols "FORT 12" and "FORT 12TP". At the same time, he noted the differences between the parameters of the cavities in the cases of the use of pistols: when fired with "FORT 12", the parameters of the cavity had a wave-like character (high indicators within the depth range of 6-10 cm) and reached a maximum at a depth of 15-23 cm, while "FORT 12TP" high cavity indicators were observed at depths of 4-10 cm and maximum at 16-24 cm.
As for the influence of layers of clothing on the parameters of gunshot damage, the opinion of the general public of scientists is unequivocal regarding the importance of taking into account the results of experimental ballistic studies using covering material on targets. Such conclusions were proved as a result of experimental studies by T. Stevenson [22] with co-authors in the study of military clothing, D. C. Kieser [8] and colleagues in the study of denim fabric and P. F. Mahoney [11] and others in the study of helmets.
The continuation of discussions regarding the optimal model for conducting a ballistic experiment was also noted. Thus, data on greater consistency of results when using a biological imitator of the human body and 20 % but not 10 % gelatin solutions were found [10], and the high value of using a support for the target during ballistic studies, especially if the target is small, was noted [19].

Conclusions
1. The use of the "AE 790G1" gun leads to the formation of a larger temporary cavity compared to the "FORT 12R".
2. All types of clothing used in the study contributed to the reduction of the temporary cavity indicators, thus showing protective properties that were most noticeable when fired from a distance of 25 cm.
3. When firing from "FORT 12R", the formation of a temporary cavity is noted, resembling in shape a jug with a wide base, which narrows sharply at the end, while when firing from "AE 790G1" a temporary cavity is formed, resembling an amphora with a thin base, which then expands and gradually narrows at the end.