Contact Shots Research Articles

On the effect of shooting distance, ballistic model construction, doping and weapon type on the simultaneous analysis of DNA and RNA from backspatter recovered from inside surfaces of firearms

Investigations at crime scenes after criminal acts involving gunshot injuries have occurred often encompass the analysis of traces of blood and so-called backspatter. Molecular genetic analysis of backspatter generated by contact shots and shots from very short distances has already been demonstrated to critically contribute to victim identification and the reconstruction of firearm-related crimes.Herein, we investigated the effect of several combinations of shooting distances and types of firearms on backspatter generation and co-extraction and simultaneous analysis of DNA and RNA isolated from traces of backspatter. Additionally, we assessed whether ‘triple contrast’ doping of ballistic models interferes with forensic analysis of DNA, mtDNA and co-extracted mRNA and miRNA from backspatter collected from inside parts of firearms generated by experimental shootings.We show the effect of shooting distance and the type of firearm in experimental shootings on the yields of DNA and RNA co-extracted from backspatter and the success rates of forensic DNA profiling and RNA based organ identification. Furthermore, we demonstrate that ‘triple contrast’ stained biological samples collected from inside surfaces of firearms are amenable to forensic DNA profiling and permit analysis of the entire mtDNA D-loop even for ‘low template’ DNA amounts that preclude standard short tandem repeat DNA analysis.

Detectability and medico-legal value of the gunshot residues in the intracorporeal channel

The application of the histochemical stain of sodium rhodizonate to the entrance wound for the detection of the lead (Pb) residues coming from the gunshot may be affected by false positive cases due to the contamination of the environmental Pb. The aim of the Authors is to histochemically search the Pb of GSR in a region which should be more protected by the contamination: the intracorporeal channel.Two hundreds and eighteen serial histological specimens of the intracorporeal channels coming from 25 subjects (dead due to gunshots and being autopsied at the Section of Legal Medicine of the Milan University, in the years 2013–2014) were stained with the sodium rhodizonate and sodium rhodizonate in acid environment (HCl 5%), and then observed by the microscope.The sodium rhodizonate showed a positivity for the Pb residues in the intracorporeal channel, with the detection of the particles within the first 2 cm beyond the entrance wound in 6 cases over the total number of 25 (24%). Victims were characterized by common features: short-barreled weapon; contact shots or short-distance shots; involvement of regions that were not covered by clothing; preservation of the microscopic structure of organs interested by the intracorporeal channel.The searching of GSR in the intracorporeal channel, even in conditions securing a high sensitivity, could represent an important test for the discrimination between an environmental contamination of Pb and the presence of Pb residues by GSR: once confirmed the presence of GSR in the intracorporeal channel by the histochemical analysis, the diagnostic process should require the application of the SEM-EDX for the confirmation of the results. Although not yet studied, this combination could be applied to cadavers exposed to the environment, with advanced post-mortal phenomena permitting at least the suspects of the existence of gunshot wounds at the macroscopic autopsy evaluation. Indeed, in some cases, the putrefaction is so advanced that no suspect of gunshot injuries could be derived from the soft tissue.

Simultaneous analysis of nuclear and mitochondrial DNA, mRNA and miRNA from backspatter from inside parts of firearms generated by shots at "triple contrast" doped ballistic models.

When a firearm projectile hits a biological target a spray of biological material (e.g., blood and tissue fragments) can be propelled from the entrance wound back towards the firearm. This phenomenon has become known as "backspatter" and if caused by contact shots or shots from short distances traces of backspatter may reach, consolidate on, and be recovered from, the inside surfaces of the firearm. Thus, a comprehensive investigation of firearm-related crimes must not only comprise of wound ballistic assessment but also backspatter analysis, and may even take into account potential correlations between these emergences. The aim of the present study was to evaluate and expand the applicability of the "triple contrast" method by probing its compatibility with forensic analysis of nuclear and mitochondrial DNA and the simultaneous investigation of co-extracted mRNA and miRNA from backspatter collected from internal components of different types of firearms after experimental shootings. We demonstrate that "triple contrast" stained biological samples collected from the inside surfaces of firearms are amenable to forensic co-analysis of DNA and RNA and permit sequence analysis of the entire mtDNA displacement-loop, even for "low template" DNA amounts that preclude standard short tandem repeat DNA analysis. Our findings underscore the "triple contrast" method's usefulness as a research tool in experimental forensic ballistics.

Simulating backspatter of blood from cranial gunshot wounds using pig models.

Few studies have examined the biomechanical basis for backspatter from cranial gunshot wounds. Backspatter is material which travels against the direction of fire following ejection from a gunshot entrance wound. Our paper focuses on the use of animals for reconstructing this phenomenon. Five live pigs and several slaughtered pigs were shot using either 9 × 19mm, 115 grain, full metal jacketed ammunition or .22 long rifle, 40 grain, lead, round-nose ammunition. A high-speed camera was used to record the entrance wound formation and backspatter. A small amount of backspattered material was produced with all targets, and blood backspatter was seen in a few cases. However, we conclude that our model provides an understanding of the phenomenon of backspatter and the physical mechanisms associated with it. The various components of the mechanism of backspatter formation are complex and overlap. The principle mechanism observed in pig cranial gunshots was the high-speed impact response of the skin overlying the skull bone. This study has also produced evidence supporting the view that backspatter can result from the splashing of superficial blood if it is already present on the skin. Subcutaneous gas effects have been demonstrated for backspatter from contact shots. There has been no clear evidence of the role of the collapse of a temporary cavity within the brain.

The 'triple contrast' method in experimental wound ballistics and backspatter analysis.

In practical forensic casework, backspatter recovered from shooters' hands can be an indicator of self-inflicted gunshot wounds to the head. In such cases, backspatter retrieved from inside the barrel indicates that the weapon found at the death scene was involved in causing the injury to the head. However, systematic research on the aspects conditioning presence, amount and specific patterns of backspatter is lacking so far. Herein, a new concept of backspatter investigation is presented, comprising staining technique, weapon and target medium: the 'triple contrast method' was developed, tested and is introduced for experimental backspatter analysis. First, mixtures of various proportions of acrylic paint for optical detection, barium sulphate for radiocontrast imaging in computed tomography and fresh human blood for PCR-based DNA profiling were generated (triple mixture) and tested for DNA quantification and short tandem repeat (STR) typing success. All tested mixtures yielded sufficient DNA that produced full STR profiles suitable for forensic identification. Then, for backspatter analysis, sealed foil bags containing the triple mixture were attached to plastic bottles filled with 10% ballistic gelatine and covered by a 2-3-mm layer of silicone. To simulate backspatter, close contact shots were fired at these models. Endoscopy of the barrel inside revealed coloured backspatter containing typable DNA and radiographic imaging showed a contrasted bullet path in the gelatine. Cross sections of the gelatine core exhibited cracks and fissures stained by the acrylic paint facilitating wound ballistic analysis.

Muzzle imprint mark: A patterned injury which may be constituted of intradermal blood extravasations

The muzzle imprint mark in contact shots is usually regarded as a patterned pressure abrasion depicting the barrel end as well as adjacent constructional components of the weapon. Due to parching after exposure to air, the affected skin assumes a brown color, especially along the contours of the impacting structures. Apart from this well-known type of epidermal damage, the imprint mark may also be formed by intradermal hemorrhages. In some cases, these intracutaneous bleedings manifest themselves as circular, curved or straight reddish lines mirroring the surface relief of the weapon's muzzle end. To estimate the frequency of skin hematomas in muzzle imprints, 35 consecutive contact shots to the head (temple, forehead, submental and occipital region) were evaluated. In 3 cases, the muzzle imprint mark exclusively consisted of intracutaneous bruises surrounding the bullet entrance hole. In 14 cases, the muzzle imprint was composed of both excoriations and intradermal hematomas.

Persistence of Biological Traces at Inside Parts of a Firearm from a Case of Multiple Familial Homicide

Backspatter from wounds caused by contact shots against a biological target had before been shown to be propelled into firearms' barrels where they can persist and be retrieved from as relevant forensic evidence. Herein, that insight was applied to the investigation of a case of multiple familial homicide with a firearm. Samples of backspatter were collected from the firearm using DNA-free swabs. DNA was extracted from the swabs, and 16 STR systems were PCR-amplified to generate DNA profiles of all victims shot by the firearm. The quality of the resulting DNA profiles was sufficient to exclude the perpetrator as donor and to differentiate the three closely related victims thereby proving that all three victims had been shot by the same firearm from very close or contact distance. A key insight gained from this case was that not only a firearms' barrel inside but other inner surfaces may be charged with profilable DNA.

Identification of gunshots to the head by detection of RNA in backspatter primarily expressed in brain tissue

Traces of backspatter recovered from the inside of the barrel of a gun that was used to deliver suicidal or homicidal contact shots may be a source of valuable forensic evidence and first systematic investigations of the persistence of victim DNA from inside firearms have been presented. The aim of the present study was to include victim RNA in such analyses to determine the origin of tissues in addition and parallel to standard DNA profiling for forensic identification purposes.In a first step, suitable mRNA (C1orf61) and micro-RNAs (miR-124a and miR-124*) that are primarily expressed in brain tissue were selected from potential candidates and confirmed using quantitative PCR (qPCR). Secondly, a co-extraction procedure for RNA and DNA was established and brain differentiability of the selected RNAs was demonstrated via qPCR using samples from experimental shots at ballistic models. In a third step, this procedure was successfully applied to analyse samples from real casework comprising eight cases of suicidal contact shots. In this pilot study, we are first to report the possibility of co-extracting mRNA, miRNA and DNA from ballistic trace samples collected from the inside of firearms and we demonstrate that RNA and DNA based analyses can be performed in parallel to produce informative and highly complementary evidence.

Persistence of biological traces in gun barrels after fatal contact shots

In the majority of cases suicidal shots are put to the head. Typically the gun's muzzle is held against the head. The aim of the present prospective study was to investigate whether victim DNA could reliably be recovered from the inside of the barrels of firearms that were used in 20 cases of homicidal or suicidal close contact shots. Additionally, it was investigated whether such biological traces were eliminated by subsequent firing. After autopsy sterile swabs were used to collect samples from the anterior part of the barrel thereby avoiding the muzzle. In some cases prior endoscopic inspection had revealed traces of blood and soft tissue in the barrel. For 16 cases, another swab was used to also collect sample from the posterior part of the barrel entering from its rear end. Then one shot was fired through the weapon using the same ammunition as in the suicidal shot and the sampling procedure was repeated. DNA was extracted using a magnetic beads based protocol, quantified, and STR-systems were amplified using several commercially available multiplex-STR-PCR-kits. For samples taken after the first shot DNA-analysis yielded STR profiles eligible for reliable individualization in 17 of 20 cases. After a second shot had been fired 8 or more STR systems were amplified successfully in 14 of 20 barrels.

Persistence of biological traces in gun barrels—an approach to an experimental model

Traces of backspatter in gun barrels after homicidal or suicidal contact shots may be a valuable source of forensic evidence. Yet, a systematic investigation of the persistence and durability of DNA from biological traces in gun barrels is lacking. Our aim was to generate a realistic model to emulate blood and tissue spatters in gun barrels generated by contact gunshots at biological targets and to analyse the persistence and typability of DNA recovered from such stains. Herein, we devise and evaluate three different models for the emulation of backspatter from contact shots: a gelatine-based model with embedded blood bags, a model based on a spongious matrix soaked with blood and covered with a thin plastic membrane and a head model consisting of an acrylic half sphere filled with ballistic gelatine and with blood bags attached to the sphere under a 3-mm silicone layer. The sampling procedure for all three models: a first shot was fired with several types of guns at each model construction and subsequently a second shot was fired at a backstop. Blood samples were collected after each shot by probing the inner surface of the front and rear end of the respective gun barrel with a sterile swab. DNA was then extracted and quantified and up to 20 different short tandem repeat (STR) systems were amplified to generate DNA profiles. Although DNA quantity and STR typing results were heterogenous between the models, all models succeeded in delivering full STR profiles even after more than one shot. We conclude that biological traces in gun barrels are robust and accessible to forensic analysis and that systematic examination of the inside of gun barrels may be advisable for forensic casework.

Wounding capacity of muzzle-gas pressure

Suicidal gunshot wounds that are caused by ammunition fired from a 9-mm Luger pistol, with direct contact between the gun muzzle and the victim's head, present a serious injury pattern even with full metal jacket bullets. Wound ballistic experiments were performed to clarify whether muzzle gases from the firearm have an additional wounding potential. Fifteen head models were prepared as follows: an acryl sphere measuring 14 cm in diameter was completely covered with a layer of silicon that was 3 mm thick. These spheres were filled with 10% gelatine. At 4°C, these models were fired at with a 9-mm Luger pistol, loaded with Quick Defense 1 expanding bullets. Five shots were fired with direct muzzle contact, one shot was fired from a distance of 10 cm, four shots were fired from a distance of 2 m, and five shots were fired from a distance of 4 m. Each projectile penetrated the model; all but one projectile deformed regularly. Each acryl sphere shattered into comminuted pieces but was held together by the silicon cover. The gelatine filling was then cut into slices 1 cm thick, and each slice was optically scanned. An evaluation was performed following both Fackler's Wound Profile method and the polygon procedure method. The pattern of gelatine disruption did not differ in shots from intermediate ranges, but the amount of gelatine destruction was always more extended in the case of muzzle contact shots. Depending on the section of the bullet path, crack lengths were 31% to 133% longer in contact shots. The first centimetre and the second half of the bullet path showed the greatest increase. The experimental findings prove the wounding capacity of muzzle gases.

GSR deposition along the bullet path in contact shots to composite models

In contact shots, all the materials emerging from the muzzle (combustion gases, soot, powder grains, and metals from the primer) will be driven into the depth of the entrance wound and the following sections of the bullet track. The so-called "pocket" ("powder cavity") under the skin containing soot and gunpowder particles is regarded as a significant indicator of a contact entrance wound since one would expect that the quantity of GSR deposited along the bullet's path rapidly declines towards the exit hole. Nevertheless, experience has shown that soot, powder particles, and carboxyhemoglobin may be found not only in the initial part of the wound channel, but also far away from the entrance and even at the exit. In order to investigate the propagation of GSRs under standardized conditions, contact test shots were fired against composite models of pig skin and 25-cm-long gelatin blocks using 9-mm Luger pistol cartridges with two different primers (Sinoxid® and Sintox®). Subsequently, 1-cm-thick layers of the gelatin blocks were examined as to their primer element contents (lead, barium, and antimony as discharge residues of Sinoxid® as well as zinc and titanium from Sintox®) by means of X-ray fluorescence spectroscopy. As expected, the highest element concentrations were found in the initial parts of the bullet tracks, but also the distal sections contained detectable amounts of the respective primer elements. The same was true for amorphous soot and unburned/partly burned powder particles, which could be demonstrated even at the exit site. With the help of a high-speed motion camera it was shown that for a short time the temporary cavitation extends from the entrance to the exit thus facilitating the unlimited spread of discharge residues along the whole bullet path.

Patterned imprint mark due to the folded shoulder stock: A possible finding in contact shots from submachine guns

The muzzle imprint (barrel mark) is a pressure abrasion typically associated with contact shots. Apart from the contours of the actual muzzle profile, other constructional parts such as the front sight and/or the recoil spring guide of semiautomatic pistols may be imprinted next to the bullet entrance wound. In some types of submachine guns the shoulder stock can be folded forward so that its end partly encircles the muzzle. If such a weapon was in contact with the skin at the instant of discharge, a corresponding contusion mark is to be expected. The imprint configuration may point to the type of weapon and to the way in which the gun had been held when firing the shot. The paper presents the injury pattern in a 36-year-old man who committed suicide with a Scorpion SA Vz 61 submachine gun cal. 7.65 mm Browning from former Czechoslovakia.

Effect of shortening the barrel in contact shots from rifles and shotguns

In a suicidal gunshot fired to the chest from a carbine, the barrel of which had been shortened to half its original length, an unexpectedly large degree of destruction of the anterior thoracic wall with extensive undermining of the subcutis was found. This phenomenon was investigated for reconstructive purposes by firing test shots from two different long guns (caliber 7.92 x 57 repeating rifle with full-jacketed pointed bullet and caliber 12/70 single-barreled shotgun with shotgun slug) into blocks of soap (38 x 25 x 25 cm). The contact shots were fired before and after shortening the barrels (repeating rifle from 60 to 30 cm and single-barreled shotgun from 72 to 36 cm). The volume of the cavities in the simulant was visualized three-dimensionally with the help of a multislice computed tomography (CT) scanner and calculated sectionally. With the repeating rifle and the single-barreled shotgun, the shots from the sawed-off barrels produced significantly larger cavity diameters in the first section of the bullet track. This effect is attributable to the fact that, with a shortened barrel, the gas pressure at the muzzle is higher, thus, leading to increased expansion in the initial part of the wound track in contact shots.

Gunshot injuries as a topic of medicolegal research in the German-speaking countries from the beginning of the 20th century up to the present time

The 100th anniversary of the foundation of the German Society of Legal Medicine is a good opportunity to review its contributions to forensic wound ballistics. The present article gives an overview of the scientific development in this field with special emphasis on work pioneering new developments and findings valid up to the present day, for example the presence of carboxyhemoglobin in the vicinity of the entrance wound as a sign of a contact or close-range shot [A. Paltauf, Wien. Klin. Wochenschr. 3 (1890) 984–991, 1015–1017]; the correct interpretation of the muzzle imprint [A. Werkgartner, Beitr. Gerichtl. Med. 6 (1924) 148–161] and the retrograde ballooning of the bullet entrance region in contact shots [F. Hausbrandt, Dtsch. Z. ges. Gerichtl. Med. 38 (1944) 45–76; H. Elbel, Med. Welt 20 (1958) 343–345]; wound patterns from captive-bolt livestock stunners [H. Czursiedel, Dtsch. Z. ges. Gerichtl. Med. 28 (1937) 132–133]; singeing of synthetic fiber textiles in close-range shots with nitro powder ammunition [S. Berg, Arch. Kriminol. 124 (1959) 5–8,17–22]; the wound ballistic processes on penetration of the bullet and the origin of the abrasion collar [K. Sellier, Beitr. Gerichtl. Med. 25 (1969) 265–270]. More recently medicolegal research in the German-speaking countries covered the following subjects: studies of the dynamic bullet-target interactions in experimental gunshots to simulants and composite body models; use of modern imaging techniques (CT, MRI) in the pre-autopsy diagnosis of lethal gunshot injuries; injuries from blank guns; mechanisms of incapacitation by gunshot injuries; development of improved methods for the evidence of gunshot residues on the firing hand; backspatter from close-range shots; medicolegal contributions in the discrimination of accidental, homicidal and suicidal gunshot injuries.

Skin tears away from the entrance wound in gunshots to the head

The present investigation covers 116 contact shots to the head and shots into the mouth from the Freiburg forensic autopsy material including 20 gunshot wounds which showed stretchmark-like tears of the facial skin away from the entrance wound. In these cases the gunshot entrance wounds were localised either in the mouth, the forehead, or the submental region. The stretchmark-like tears were found in the region of the eyes and the nasolabial folds. Radial tears were seen on the lips and in the vicinity of the corners of the mouth, particularly in cases involving shots into the mouth. The stretchmark-like tears essentially followed the skin tension lines and the expression-related lines of the face. They were apparently caused by the subcutaneous or intraoral expansion of the muzzle gases and/or the radial forces of the bullet resulting in ballooning and overextension of the facial soft tissues. The weapons used were not only rifles and shotguns, but also revolvers and pistols.

Fatalities from black powder percussion handguns

Three suicides and one homicide from black powder muzzle loading handguns are reported and the muzzle velocities of two weapons are recorded. The fatal head shots caused wide wound tracts traversing the brains and intracerebral haemorrhages remote from the tract were present in every case. The skulls showed considerable fractures which were pronounced in the cases of contact shots but were also present when the range of fire was 5 m. These extensive injuries from soft lead spheres with muzzle velocities of only approximately 200 m/s are attributed to the expansion of the spheres. The regularly occurring deformation resulted in 13-16 mm calibre missiles in the cases of .44 spheres. The special features of black powder such as incomplete and slow combustion resulted in intense soot deposits in the vicinity of the entrance wound and in long ranges the gunshot residues travelled. In contact shots, large pocket-like underminings even in deeper tissue layers, abundant soot along the trajectory and skin burns were observed.

Fatalities from black powder percussion handguns

Three suicides and one homicide from black powder muzzle loading handguns are reported and the muzzle velocities of two weapons are recorded. The fatal head shots caused wide wound tracts traversing the brains and intracerebral haemorrhages remote from the tract were present in every case. The skulls showed considerable fractures which were pronounced in the cases of contact shots but were also present when the range of fire was 5 m. These extensive injuries from soft lead spheres with muzzle velocities of only ∼200 m/s are attributed to the expansion of the spheres. The regularly occurring deformation resulted in 13–16 mm calibre missiles in the cases of .44 spheres. The special features of black powder such as incomplete and slow combustion resulted in intense soot deposits in the vicinity of the entrance wound and in long ranges the gunshot residues travelled. In contact shots, large pocket-like underminings even in deeper tissue layers, abundant soot along the trajectory and skin burns were observed.

Multiple gunshot suicides: potential for physical activity and medico-legal aspects.

Out of 138 clearly defined gunshot suicides which were autopsied, 11 persons (8%) fired two or more gunshots to the body. From these 11, 5 cases involved 2 gunshots to the head where the bullets fired first had missed the brain. The trajectories were restricted to the chest in three cases and a combination of gunshots to the head and chest including two perforating heart wounds without immediate incapacitation occurred in three more cases. Reliable incapacitation is based on physiological effects (tissue disruption) and can only be achieved by decreasing the functioning capability of the CNS. This can be accomplished by direct disruption of brain tissue or indirectly by cerebral hypoxemia from massive bleeding. Targets of immediate incapacitation are restricted to certain CNS areas and targets of rapid incapacitation include the heart, the (thoracic) aorta and the pulmonary artery. Other major blood vessels and major organs (lungs, kidneys, liver, spleen) constitute targets of delayed incapacitation. This general classification can be derived from the literature and is illustrated by the cases presented. A thorough post mortem can exclude or quantify the potential for physical activity. Typical features of single gunshot suicides such as contact shots, classical entrance wound sites and soot/backspatter on a hand also occur in multiple gunshot suicides.

Observations of High Velocity Bloodspatter on Adjacent Objects

In a recent homicide investigation, high velocity backspatter was observed on the sleeve cuff of the accused. These minute droplets were discovered only after microscopic examination and were limited in number. A study was initiated to determine if these were truly backspatter droplets or transferred blood produced from light contact with a bloody item. It was observed that the backspattered blood was primarily limited to contact or near contact shots. An exception was a shot into an already bloody surface. It was found that backspattered blood would deposit on the shooter's shirt sleeve irrespective of the weave pattern. Transferred blood was observed only on the fiber tops. This information was found to be useful in reconstruction of events in suicides as well as possible homicides.