Forensic characteristics of injuries sustained during the explosion of defensive grenades

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BACKGROUND

The incidence of injuries caused by explosions of various explosive devices has been steadily increasing in recent years [1–3]. Consequently, explosive injury remains a pressing issue in forensic medicine. Currently, forensic pathologists have limited tools to differentiate the type of explosive device and determine the distance to the explosion epicenter based on the morphological characteristics of injuries on the victim’s body and clothing. This underscores the need for further research and the development of differential diagnostic criteria for injuries resulting from the detonation of various types of grenades [4–6].

Fragmentation hand grenades remain the most commonly used explosive devices. They are categorized as:

• defensive
• offensive
• anti-tank.

Among defensive grenades, the most widely used are the F-1 (time-delay defensive hand grenade) and RGO (defensive fragmentation hand grenade).

The F-1 grenade has a cast-iron body shaped as an ellipsoid with a wall thickness of 4–9 mm and features three circumferential and eight longitudinal grooves. It contains 50–56 g of TNT as the explosive charge and is detonated using UZRGM¹ (UZRGM²) fuzes. According to current scientific sources, the explosion of this grenade produces approximately 1000 fragments weighing 0.1–1 g (with fragments over 0.8 g comprising about 4%). The fragments are irregularly shaped and disperse at a velocity of 700–800 m/s.

The total damage range is approximately 35–50 m, with an effective damage range of about 4–5 m [7].

The RGO grenade has a steel body with pre-formed fragmentation grooves. It is charged with approximately 90 g of TNT-RDX mixture and employs a UDZ³ fuze. Upon detonation, the grenade produces 650–700 fragments weighing 0.4–0.45 g, dispersing at approximately 1200 m/s. The total damage range is 50–100 m, while the effective damage range is approximately 12–20 m [7].

AIM

This work aimed to identify characteristic morphological features of injuries to clothing fabric and a biological human body simulator caused by the detonation of F-1 and RGO fragmentation hand grenades.

METHODS

Study Design

It was a single-center, cross-sectional, uncontrolled experimental study.

Study Setting

Explosions of F-1 and RGO hand grenades were carried out in the field at a specialized testing range. The primed grenades were fixed in soil depressions and detonated remotely using a braided cord attached to the fuze ring. The biological target was a human body simulator, i.e. porcine forelegs with skin intact (no hair or thermal treatment), fixed to rigid particleboard substrates measuring 0.43 × 0.40 m. Each biological target was wrapped in white cotton fabric (calico) blended with up to 5% viscose, measuring 0.4 × 0.7 m. Explosions were performed at fixed distances: in contact, and at 20, 50, and 100 cm from the target, which was positioned 20 cm above the level of the explosive device. A total of 24 targets were examined (3 per each test series). Macroscopic and microscopic examinations were conducted using a Hitachi FlexSem 1000 II® scanning electron microscope (Hitachi HT, Japan) and a Bruker Quantax 80® energy-dispersive X-ray spectrometer (Bruker Physik AG, Germany). Scanning was performed in low-vacuum mode (VP-SEM 30 Pa) at magnifications ranging from ×45 to ×650. The accelerating voltage was 15 kV, the absorbed current was 600–800 pA, and the working distance was 12 mm. Spectra were acquired automatically until statistically reliable data (1 million counts) were obtained. Visual macroscopic analysis included morphological assessment of grenade fragments, determination of their elemental composition, and elemental mapping (chemical element distribution maps). Prior to scanning electron microscopy with energy-dispersive X-ray spectroscopy, large soft tissue residues were removed from the grenade fragments extracted from the biological target, followed by double degreasing in acetone.

Ethics Approval

Ethics approval was not required as no laboratory animals were used in this study.

Statistical Analysis

Sample size was not pre-calculated.

Statistical data analysis involved frequency assessment of identical diagnostic findings. Feature prevalence was calculated as the ratio of its frequency to the total number of observations within the group and equaled 1. Statistical processing of the elemental composition data of the fragments was performed automatically using the software of the Bruker Quantax 80® energy-dispersive X-ray spectrometer (Bruker Physik AG, Germany).

RESULTS

A contact detonation of the F-1 grenade resulted in fragmentation of the biological and fabric targets, with fragments scattered within a radius of up to 14 meters. Some fragments were not found. Recovered fragments of cotton fabric with frayed edges measured between 2 × 1 cm and 30 × 25 cm, and some showed continuous black soot deposition. The biological fragments included soft tissue, bone fragments ranging from 0.7 × 0.5 cm to 5 × 3 cm, and soft tissue containing bone fragments. Some displayed continuous black soot coverage (Fig. 1, a).

 

Fig. 1. A view of cotton fabric and fragments of a human body simulator during a contact explosion of F-1 (a) and RGO (b).

 

At a detonation distance of 20 cm, the F-1 grenade caused uniform black soot deposition on both the fabric and biological target. The cotton fabric sustained numerous defects (35 ± 7), evenly distributed across the surface, ranging in shape from round to stellate, and in size from 0.1 × 0.1 cm to 1 × 0.7 cm. The defects had frayed, irregular edges with central fabric loss. The biological target exhibited multiple (≥ 40) blind-ended injuries of round or oval shape, ranging from 0.1 × 0.1 cm to 0.7 × 0.5 cm, with peripheral black soot deposition. Fragments retrieved from the distal ends of wound tracks measured from 0.1 × 0.1 cm to 0.7 × 0.5 × 0.5 cm (Fig. 2, a).

 

Fig. 2. View of fragments from F-1 and RGO grenades: a, fragments extracted from a biological simulator of the human body after the explosion of F-1 grenade at a distance of 20 cm from the target; b, fragments extracted from a biological target after the contact explosion of RGO grenade.

 

At 50 cm, the F-1 grenade produced continuous dark gray soot deposition on the fabric and light gray soot on the biological target. Through-and-through injuries (17 ± 3) of the fabric target, mainly in the middle and lower thirds, were round, linear, stellate, or L-shaped, ranging in size from 0.1 × 0.2 cm to 6.5 × 1.5 cm, with frayed and mismatched edges. Multiple injuries in the biological target (≥ 15–18) were primarily blind-ended (probability = 0.8) and, less frequently, tangential (probability = 0.2), oval or round in shape, measuring 0.2 × 0.3 cm to 5.5 × 4.5 cm. Soot deposition was noted on periphery and along the wound tract (Fig. 3, a). Fragments retrieved from the distal ends of wound tracks measured 0.2 × 0.2 × 0.1 cm to 0.5 × 0.4 × 0.3 cm.

 

Fig. 3. A type of biological simulator of the human body: а, when an F-1 grenade explodes at a distance of 50 cm; b, when an RGO grenade explodes at a distance of 100 сm.

 

At a distance of 100 cm, the F-1 grenade produced light gray soot deposition uniformly covered the target surfaces. Through-and-through injuries (5 ± 2) of the fabric, primarily in the middle and lower thirds, were round or oval with frayed, mismatched edges. Their dimensions ranged from 0.4 × 0.6 cm to 1.2 × 0.8 cm. Notably, the lower third of the fabric surface contained multiple (≥ 5) irregularly rectangular dark gray metallic fragments, measuring from 0.1 × 0.1 cm to 0.2 × 0.3 × 0.1 cm. The biological target had 3–5 tangential or blind-ended injuries, oval or slit-like, measuring 0.3 × 0.3 cm to 2 × 1.5 cm. Retrieved fragments at the distal ends of the wound tracts ranged from 0.4 × 0.2 cm to 0.6 × 0.5 cm.

A contact detonation of the RGO grenade resulted in uniform black soot deposition on the fabric and biological targets. The fabric exhibited lacerated damage with frayed edges, with flap sizes ranging from 1.5 × 2.5 cm to 13 × 5 cm, and a prominent defect measuring 12 × 8 cm. The biological simulator revealed extensive injury with macerated, detached wound edges and a pronounced soft tissue defect. Complete oblique fractures of the bones without bone loss were also observed (see Fig. 1, b). Multiple rectangular metallic fragments measuring 0.5 × 0.5 × 0.1 cm to 2 × 1.5 × 0.1 cm were embedded in soft tissues (see Fig. 2, b).

At 20 cm, the RGO grenade caused continuous gray soot on the fabric and light gray soot on the biological target. Multiple through-and-through injuries of the tissue target (≥ 40), evenly distributed, displayed various outlines—round, linear, or L-shaped. They measured 0.5 × 0.2 cm to 6.5 × 1.5 cm and showed mismatched edges. Frayed and severed fibres of varying lengths were present along the wound edges. The biological target sustained ≥ 22 through-and-through injuries, slit-like or stellate, measuring 0.5 × 0.3 cm to 2.5 × 2.5 cm, with finely undulating mismatched wound edges.

At 50 and 100 cm, RGO grenade detonations produced no significant difference in soot deposition or wound morphology. Patchy pale gray soot was noted on the fabric, but was absent on the biological target. Isolated perforating injuries (1–3), mostly in the lower third of the fabric, were linear or L-shaped, measuring 0.5 × 0.3 cm to 3 × 1.6 cm, with matched edges with frayed and severed fibres of varying lengths. On the biological simulator, 1–3 injuries were slit-like or irregularly oval, mostly superficial blind-ended (probability = 0.8), and ranged from 0.5 × 0.3 cm to 3 × 2 cm. The wound edges were relatively smooth but mismatched (tissue defect), with peripheral gray soot deposition. Grenade metal shell fragments retrieved from the distal ends of wound tracks were quadrangular, 0.2 × 0.2 cm in size and 0.1 cm thick, and exhibited magnetic properties (see Fig. 3, b).

Scanning electron microscopy and energy-dispersive X-ray spectroscopy revealed characteristic surface features and elemental composition of the grenade fragments. F-1 fragments primarily contained iron and carbon with traces of aluminum, consistent with carbon steel. RGO fragments were composed mainly of iron with minor zinc content.

Differential diagnostic criteria for injuries caused by F-1 and RGO fragmentation hand grenades at varying distances, along with fragment characteristics and elemental composition, are summarized in Table 1.

 

Table 1. Differential diagnostic criteria for damage caused by damaging factors during the explosion of F-1 and RGO hand fragmentation grenades at various distances, fragments and their elemental composition

F-1 Grenade	RGO Grenade
Contact detonation
Target fragmentation Fragments consist of soft tissues, bone splinters, and mixed soft-tissue/bone fragments Intense soot deposition	Uniform black soot deposition across the entire surface Single extensive injury with macerated and detached wound edges Pronounced soft tissue defect Complete oblique-transverse bone fractures without loss of bone tissue
Detonation at 20 cm
Uniform, continuous soot deposition Multiple (≥40) blind-ended injuries Round or oval shape with central tissue loss Injury dimensions: 0.1 × 0.1 to 0.7 × 0.5 cm Peripheral black soot deposition	Uniform gray soot deposition Multiple (≥22) through-and-through injuries Slit-like or stellate in shape Injury dimensions: 0.5 × 0.3 to 2.5 × 2.5 cm Finely undulating, mismatched wound edges
Detonation at 50 cm
Continuous dark gray soot deposition Multiple (≥15–18) blind-ended or tangential injuries Round or oval shape Injury dimensions: 0.2 × 0.3 to 5.5 × 4.5 cm Black soot deposition on periphery and along the wound tracts	Patchy pale gray soot deposition Isolated (1–3) superficial blind-ended or through-and-through injuries Slit-like or irregularly oval in shape Injury dimensions: 0.5 × 0.3 to 3 × 2 cm Relatively smooth but mismatched wound edges Gray soot deposition at the wound periphery
Detonation at 100 cm
Uniform light gray soot deposition Isolated (3–5) tangential or blind-ended injuries Oval or slit-like with central tissue defect Injury dimensions: 0.3 × 0.3 to 2 × 1.5 cm	Injuries exhibited similar characteristics to those observed at 50 cm detonation distance
Fragment characteristics
Various geometric shapes Various sizes	Predominantly quadrangular in shape Size: 0.5 cm
Elemental composition of fragments
Iron (Fe) Carbon (C) Aluminum (Al)	Iron (Fe) Zinc (Zn)

 

DISCUSSION

This experimental study demonstrates that both the distance to the explosion epicenter and the type of explosive device can be determined based on the pattern of soot deposition and the morphological characteristics of damage to fabric and biological targets. These findings may be applied to forensic investigations of injuries sustained from the detonation of defensive fragmentation hand grenades (F-1 and RGO).

CONCLUSION

This experimental study established the distinct features of soot deposition and the morphological characteristics of injuries to cotton fabric and a biological human body simulator caused by the detonation of F-1 and RGO defensive grenades. Scanning electron microscopy and energy-dispersive X-ray spectroscopy revealed the typical chemical composition of the grenade fragments.

ADDITIONAL INFORMATION

Authors’ contribution: V.A. Kuzmina: data collection, writing—original draft; writing—review & editing; S.V. Leonov: data collection, writing—review & editing; P.V. Pinchuk, A. A. Khalikov: writing—review & editing. Thereby, all authors provided approval of the version to be published and agree to be accountable for all aspects of the work in ensuring that questions related to the accuracy or integrity of any part of the work are appropriately investigated and resolved.

Ethics approval: Ethical approval was not sought for the present study because the study did not involve laboratory animals.

Funding sources: No funding.

Disclosure of interests: The authors have no relationships, activities or interests for the last three years related with for-profit or not-for-profit third parties whose interests may be affected by the content of the article.

Statement of originality: When creating this work, the authors did not use previously published information (text, illustrations, data).

Data availability statement: The editorial policy on data sharing does not apply to this work.

Generative AI: Generative AI technologies were not used for this article creation.

Provenance and peer-review: This article was submitted to the Journal on an unsolicited basis and reviewed according to the usual procedure. Two external reviewers, a member of the editorial board, and the scientific editor of the Journal participated in the peer-review.

 

¹ Universal Modernized Hand Grenade Fuze (UZRGM) is a fuze model containing a slow-burning, low-gas pyrotechnic composition with high combustion stability, housed in an aluminum sleeve, and an azide detonator capsule enclosed in an aluminum casing.

² Universal Modernized Hand Grenade Fuze-2 (UZRGM-2) is a fuze model equipped with a less hygroscopic delay composition, featuring a combustion rate that is independent of ambient temperature.

³ Impact-Time Fuze (UDZ) is a mechanical fuze designed for the detonation of fragmentation-blast hand grenades.

About the authors

Vera A. Kuzmina

Chief State Center for Forensic Medicine and Forensic Expertise 111

Email: kuzminava@yandex.ru
ORCID iD: 0000-0003-0694-673X
SPIN-code: 1167-4112

MD, Cand. Sci. (Medicine)

Russian Federation, 3 Hospital sq, Moscow,105094

Sergey V. Leonov

Chief State Center for Forensic Medicine and Forensic Expertise 111; Russian University of Medicine

Author for correspondence.
Email: sleonoff@inbox.ru
ORCID iD: 0000-0003-4228-8973
SPIN-code: 2326-2920

MD, Dr. Sci. (Medicine), Professor

Russian Federation, 3 Hospital sq, Moscow,105094; Moscow

Pavel V. Pinchuk

Chief State Center for Forensic Medicine and Forensic Expertise 111; The Russian National Research Medical University named after N.I. Pirogov

Email: pinchuk1967@mail.ru
ORCID iD: 0000-0002-0223-2433
SPIN-code: 7357-3038

MD, Dr. Sci. (Medicine), Professor

Russian Federation, 3 Hospital sq, Moscow,105094; Moscow

Airat A. Khalikov

Bashkir State Medical University

Email: airat.expert@mail.ru
ORCID iD: 0000-0003-1045-5677
SPIN-code: 1895-7300

MD, Dr. Sci. (Medicine), Professor

Russian Federation, Ufa

References

Supplementary files