Explosion-related deaths: An overview on forensic evaluation and implications

The on-site investigation in the event of an explosion plays a twofold purpose: on one hand it allows identification of the victims, while on the other hand it contributes to clarify the circumstances which caused the explosion. Unfortunately, the presence of the forensic pathologist is not always requested from the very beginning of the rescue procedures: this may result in a confused and chaotic on-site examination, complicating further operations of identification. Explosion-related deaths are characterized by widespread injuries; the environment in which the explosion took place represents an important element that must be carefully considered by the forensic pathologist [16, 20, 46, 47]. Firstly, the on-site examination is divided into either a closed or open system, as for the classification of mass disasters [8, 15, 46, 47].

In a closed system the deflagration releases an amount of mechanical energy, also amplified by deflected and ricocheted pressure waves, provoking not only direct blast injuries but even the collapse of buildings such as industrial factories or houses (Fig. 1) [46]. In an open system, such as squares, the countryside or out-of-town rural areas, blast waves can project bodies or parts of them across a large area (Fig. 2), and weather conditions, local predators and the natural decay of the dead bodies can destroy important elements and hinder forensic operations [16, 20]. The whole area may be divided into smaller subareas which should be numbered in order to facilitate the recovery operations of the victims, or parts of them, including any personal items. In both cases, the explosion might result in a total obliteration of the affected area, thus preventing a thorough investigation of the scene, which is simply no longer recognizable [21, 47]. Moreover, alterations of the crime scene can occur due to damaging effects of the area, which are usually followed by rescue operations [13, 14].

As usual, during on-site investigations, the security assessment of the site should be performed before entering the area and at the same time the police should seal off the scene so that it will remain untouched and a proper investigation can take place [19, 47]. First, it is important to take as many pictures as possible (videos are even more preferable) of the scene and the surrounding area. The conditions of the site may have been deeply modified by the fire or adverse natural events. If an appropriate computer program is used, the photographs and the scanning of the scene can provide a 3D recreation of the event and thus make it possible to accentuate important details for further forensic analyses [48]. In addition, an accurate photographic record of the victims and their visible injuries, including the location of the bodies and their distance from the explosive device must be realized [20, 21].

It is important, especially for those cases of supposed atypical suicides, to give an answer to the questions asked by the local authorities so that the forensic investigations can be promptly organized. The forensic pathologist, supported by the police investigators, should obtain a detailed examination of the victim’s background: a socio-economical and personal profile, such as prior medical history, is an essential documentation for a better interpretation of the crime’s dynamics [15, 21, 22]. At the scene, the presence of any suicide note should be established, and information concerning any past suicide attempts be collected, including whether the victim possessed expertise in relation to explosives [22, 23, 44]. This investigatory approach can allow a preliminary reconstruction of the fatal event as a means of differentiating domestic accidents and homicidal explosion-related deaths from such uncommon forms of suicide.

Finally, the analysis of the scene analysis should be performed by a specialized team with competent training in rescue procedures and death scene investigations: photographing and collecting the victim’s clothes and personal items will be helpful for the following identification operations [14, 16, 38, 41, 42].

In the event of an explosion-related death, a study protocol based on postmortem radiology, external examination, autopsy, forensic histopathology, toxicology and anthropology is mandatory. Postmortem radiology should be the first forensic procedure performed on all bodies that have been involved in an explosion. It thereby offers the possibility to improve the observation of complex pathological findings in the autopsy room [49]. Bone and metallic fragments or other foreign objects may be easily detected at whole-body postmortem computed tomography (PMCT) [50]. Postmortem radiology may reveal small metal objects that form part of the explosive device mechanism. These may be invaluable in allowing the ballistics experts to recognize the handiwork of a particular bomb-maker or terrorist group [17]. Also, threedimensional surface scanning (3DSS) and multi-detector computed tomography (MDCT) are two techniques that are used in forensic medicine for digitalizing a body or body parts, such as bones. Interestingly, these radiological techniques allow reconstruction of severely injured skulls [51]. The instrumental approach plays two major roles in the event of an explosion: firstly, images of skeletal fractures can be evaluated whenever needed. Secondly, skull and facial digital reconstructions considerably improve identification of the victims [52, 53]. Dental radiographs are also crucial information, since they are important for dental identification, postmortem profiling, and age estimations [54‐56]. Nevertheless, a complete radiographic study before the autopsy allows preservation of information for subsequent evaluations; also, it provides evidence that can guide the forensic pathologist during the autopsy.

External examination is very useful in such cases, since features of the injury patterns can be defined, and several different samples can be collected as well. Thus, forensic pathologists should collect genetic swabs, if suspicious lesions are documented on the body. Homicides may indeed be concealed by the explosion of the building where the body was set. Ballistic experts may also collect bullets, projectile fragments and evidence from explosive discharge residues from the body of the victim. Explosive traces should be analyzed by a forensic chemical expert in order to define the typology of explosive material [57]. Moreover, residual particles may be searched through the use of Scanning Electron Microscopy/Energy Dispersive X-Ray Spectroscopy (SEM/EDX), which allows different classes of particles to be defined according to their composition and images [5, 58]. Upon external examination, a thorough collection of personal items (e.g. clothes, jewels, identity cards), in association with the identification of personal descriptors such as tattoos, scars or medical devices should improve recognition of the victim. Also, the collection of fingerprints, if still available, may permit identification of the deceased.

Internal examination reveals macroscopic evidence of blast injuries. Particularly, lungs, and intestine blast injuries, major vessel lacerations and bone fractures are the most common pathological findings. Also, hyoid bone and thyroid cartilage fractures may be present. Histologic examination may help the forensic pathologist: in lungs, standard hematoxylin–eosin (HE) shows alveolar ruptures, thinning of alveolar septae, and enlargement of alveolar spaces. Other features include circumscribed subpleural, intraalveolar, and perivascular hemorrhages with a cufflike pattern. Also, Oil-Red-O (OR) histochemical staining may reveal fat embolism [12]. Furthermore, a moderate to strong hemoglobin immunoreactivity of the edema fluid within the alveolar spaces can be detected, showing a homogenous staining pattern. On the other hand, it is very important to establish the vitality of blast injuries. Thus, immunohistochemical analyses using anti-CD15, anti-IL-15 and anti-tryptase antibodies allow a precise assessment of the lesion that may have been involved in the determinism of death, representing a tool of considerable utility in explosion-related deaths [59]. Toxicological samples should also be collected; analysis may reveal toxic gases or substances inhaled or taken by the victim.

Finally, forensic pathologists should cooperate with forensic anthropologists and odontologists to improve personal identification of the victims. A dental examination carried out by a forensic odontologist is also a very important and effective method of identification, if antemortem data are available [38, 54‐56]. Dental prosthesis records (fixed and removable prosthetic appliances as well) are one of the most common records used for identification purposes. Forensic odontologists may also analyze morphological features of extraoral and intraoral structures such as lip print patterns and rugae patterns, which are important elements for recognition of victims [60]. Genetic analysis on muscle or bone samples of the victims may confirm identity, if any relative is available.

A schematic forensic assessment in the event of an explosion is shown in Fig. 3.

Suicide by using an explosive device, when not involved in a terrorist attack, is quite uncommon in medicolegal practice when compared with other routinely adopted methods [23, 44]. The case presented is a further exception, since the possibility to mistake this suicidal event with an accident or homicide relies mainly on circumstantial findings. In the literature of the last thirty years, a few case reports [7, 24‐35] and one older study from Sweden [39] about self-inflicted explosion deaths have been published. In the cases reported [7, 23‐36, 39], victims were men, ranging between 20 and 76 years-old (mean 37.7 years), and except for one case (with no risk factors described) [24], all suffered from psychiatric diseases, alcoholism, drug addiction, financial or personal problems [22‐36, 39, 44].

In the analysis performed, three different patterns of non-terrorist explosion-related suicides can be defined, as follows:

Since in these cases victims who committed suicide by this uncommon manner were males, great caution should be paid by the forensic pathologist when dealing with a case of a woman suspected of a self-inflicted explosion death. A suspicion of murder or accident should be kept in consideration, until proven otherwise.

Further considerations are required in the evaluations of the damage patterns related to explosions, considering that such injuries can easily be mistaken for shotgun wounds. Hence, the absence of a firearm and the absence of any bullets at the scene, but the presence of radiopaque fragments within the body at the postmortem radiological examination, should direct suspicion towards the use of explosive devices [22, 42, 44]. Finally, an accurate assessment of the victim’s background must be conducted in order to determine the manner of death: look for possible access to explosive materials, psychiatric disorders or any personal problems of the deceased [13, 26, 29, 61].

This subcategory of explosion-related deaths includes fatalities by explosion that occurred in a domestic setting. Among these, accidental gas leak represents a common event worldwide [1, 4, 6, 7, 11, 17‐19, 46]. The scene is characterized by building collapse, fire, debris and a cloud of dust, which make rescue operations protracted and very difficult.

At autopsy, external examination can reveal a diffusely edematous body with multiple wounds [34], mainly lacerations, many abrasions along with different degrees of burns (Fig. 4). Internal examination usually shows pulmonary injuries and injuries to the upper airways: the trachea and main bronchi are lacerated while the lungs are often hyperinflated with severe blunt-force trauma and lacerations [1, 4]. Also, traumatic asphyxia can frequently lead to death due to the massive amount of dust inhaled in the event of building collapse or to fixation of the chest by rubble [17‐19]. The abdomen can be heavily damaged with organs torn off from the abdominal wall, such as the stomach, intestines and kidneys avulsion or hepatic and splenic gross lacerations [1, 17‐19]. An additional finding is the fracture of the thyroid cartilage (Fig. 5), which is produced by the explosive barotrauma or direct violent impact. When this evidence is found, attention must be paid to avoid misinterpretation regarding homicidal strangulation [11, 17, 22]. Autopsy helps to confirm the cause of death of the victims; also, it contributes to the assessment of the manner of death. Hence, a close cooperation between the forensic pathologists and the investigators can differentiate sabotage from accidents in cases of domestic explosive-related deaths.

Work-related fatalities are a common phenomenon worldwide. Hazardous work is represented by coal mines (especially in the past for firedamp leaks), chemical industrial sites or firecracker factories, where explosions can typically occur [7, 36, 39]. In the literature, a few cases have been reported such as explosions caused by coffee-making machines, autoclave machines, or while repairing an air conditioner compressor [45]. A common pattern can be identified in the evidence that explosions derived from high-pressure appliances [7, 40, 45].

Byard described the risk of work-related explosions in the enclosed engine room of fishing vessels if volatilized fuel is not adequately removed. The flammable properties of the mixture are determined by the ratio of fuel vapor to air: the speed and magnitude of combustion can be extremely violent, resulting in an explosion [43]. Furthermore, an unusual “work-related” death occurred in Milan in 2017, when a thief died while attempting to break into an automated teller machine (ATM) using the explosive power of an acetylene gas cylinder [37]. Most of the cases were accidental events; moreover, victims frequently died after the explosive accident or within the first 24 h, reflecting the seriousness of the injuries reported by the workers [40]. The injury pattern showed a combination of blast effects, burns, and flying missile injuries which damaged internal organs. The lungs may also show subpleural patchy hemorrhages, pulmonary contusions and intrapulmonary hemorrhage (Fig. 6). The predominant site of lethal wounding was the head, followed by the chest or the combination of both [36, 37, 40, 43, 45].

In cases like the ones mentioned above, forensic examination of the dead bodies revealed mainly several burn injuries: different degrees of burns are differently distributed all over the body, including significant charring. Charred and extensively damaged bodies require a careful examination for identification purposes [20, 21, 41]. Nowadays, workplace deaths represent an important social problem [40]: the reconstruction of the event allows authorities to find out which responsibilities involved the employer and which ones the worker.

A variety of events can lead to explosions related to large transport vehicles. Aircraft accidents, such as the example reported above, railway disasters, maritime accidents and other mass disasters can be included in this category [20]. In these cases, the explosion produces a significant kinetic effect as a result of collisions between objects travelling at high speed [19]. Since the mechanical shock wave cannot dissipate the energy of the impact itself, the accumulation of heat and pressure at the contact site instantly breaks the two objects, projecting their fragments in every direction and vaporizing or partially melting the material [7, 38]. These events result in a wide number of fatalities, the remains of which, being often severely traumatized, charred and/or dismembered, need to be identified and subjected to medicolegal investigation [1, 2, 13, 20].

Two major factors complicate the recovery of human remains: body destruction and context [40]. Since explosion may lead to extreme body fragmentation, care must be taken in analysis at the scene [15, 19, 47]. Forensic analysis of remains must include assessment of minimum number of individuals and commingling issues as well as identification [17, 18, 54, 55, 56]. Identifications are frequently facilitated by recovery and analysis of identification tags, dental restorations and surgical materials [41]. The context is important since in most cases human remains are located in proximity to other materials of similar appearance [20, 21]. Ideally, forensic anthropologists should participate in the recovery since they are experts in recognizing fragmented human remains [17, 41]. In the case mentioned above, the team of experts guided by forensic odontologists succeed identifying all the victims, through consultation of the victims’ dental records, a fundamental part of the entire investigation [38, 60].

At autopsy, trauma interpretation can be difficult due to the multiplicity of skeletal and visceral injuries with a prevalence of heat-related lesions, usually complete charring and fragmentation [41]. The distinction of different injury patterns may provide important information for the investigators, since one of the priorities is to reconstruct the dynamic of the event to differentiate accidental events from sabotage.

In cases of explosive military devices, blast effects uncommonly lead to death since the terrorist bomb usually produces low energy barotrauma in close proximity to the explosion. For more powerful bombs, flash burns can occur on individuals nearby [2, 3].

The individual in contact with or near the seat of explosion can be blown to pieces and scattered by the force of explosion gases [8]. Solid fragments from the device, such as the case or the conveyance, in which the bomb was concealed (a car usually is usually the most common vehicle used), can be projected at high speed and over a wide area, hitting the bodies of people nearby [2]. Metallic pieces can act like bullets, causing significant or fatal injuries [13, 18]. In these cases, the autopsy shows a multiplicity of injuries such as a pigmented dust produced by the explosion on skin and clothing, the burning of hair and eyebrows, and the laceration and ignition of clothing [10, 21]. Also, the so-called “peppering” appearance of the skin caused by the small missiles creating the typical triad of lesions (bruises, abrasions and lacerations) can be assessed (Fig. 7) [9, 17]. The body can be totally or partially destroyed: extremities are equally involved resulting in hands, arms, feet and legs disrupted or ripped out (Fig. 8). Localized injuries at the legs and the abdominal region have been assessed on the body of the terrorist when a premature deflagration occurs [8, 14, 42]; it can be an important element to be considered in order to distinguish between bombers and suicidal attacks. The number and distribution of fractures can help the differentiation of injury mechanisms, as they are relevant criteria for distinguishing an explosive charge carrier from a victim [13, 18, 42]. According to the literature, multiple injuries resulted in the cause of death, followed by localized injuries at the head, then the chest and the abdomen [6, 8, 14].

Various ballistic and forensic experts may be involved in terrorist events; among them, chemists and engineers will have the task of determining the composition and position of the device. The forensic pathologist can be part of the event reconstruction, as localized severe trauma indicates the relative position of the bomb and the victim at the time of detonation [14]. Trace evidence of explosive residues can be found on the bodies and further analyzed [5]. In this way, investigations can receive a fundamental support in identifying also the bomb-carrier and, thus, the precise dynamics of the event [17, 18, 42]. In the case mentioned above, starting from the autopsy reports, the team of experts in charge managed to develop a visual record placing each victim in the most probable position at the time of the explosion, playing a pivotal role in the forensic proceedings.