backspatter in close range shots with 12 … · were investigated on the shot-gun after each shot....

37 Adli Tıp Dergisi / Turkish Journal of Forensic Medicine, Cilt / Vol.:24, Sayı / No:3

ABSTRACT

In criminal cases involving fire-arms, it is likely to detect residu-es belonging to the target on the firearm itself. In order to inves-tigate the backspatter from the target, the present study aims to detect the residues belonging to the target by firing test shots from predetermined distances.

Test shots were fired at lamb li-vers and lime with a shotgun and

residues belonging to the target were investigated on the shot-gun after each shot. Subsequent to the shots fired at the liver, a commercial kit named Bluestar, a new Luminol derivative, was used to detect the biological re-sidues on the shotgun.

Among the shots fired at the li-ver, blood stains were detected in the barrel of the shotgun in those fired at a distance of 60 cm or less and on the barrel in those fired at a distance of 30 cm

or less. Among the shots fired at lime, on the other hand, lime was detected in the barrel in the shots fired at a distance of 120 cm or less. However, spatter of lime droplets on the barrel was observed only in the test shots fired at a distance of 100 cm or less. Thus, it was concluded that the investigation of residues be-longing to the target should be a part of the criminal investigation.

Key words: shotgun, backspat-ter, Luminol

> Prof.Dr. Yücel ARISOY1

1 Dokuz Eylül Üniversitesi Tıp Fakültesi Adli Tıp AD. İzmir

12 KALİBRE AV TÜFEĞİ İLE YAPILAN YAKIN ATIŞLARDA NAMLUDAKİ LEKELER

Backspatter in Close range Shots with 12 Gauge Shotgun

BACKSPATTER IN CLOSE RANGE SHOTS WITH 12 GAUGE SHOTGUN

ÖZET

Ateşli silahlarla gerçekleşti-rilen kriminal olaylarda, bazı balistik incelemeler, rutin olarak yapılır. Bunların birisi hedef üzerinde atış artıkları-nın aranmasıdır. Buna kar-şılık silah üzerinde de hedefe ait kalıntıların bulunabilmesi mümkündür. Hedeften geri-ye sıçramayı araştırmak için belirli mesafelerden deneme atışları yapılarak silah üzerin-de hedefe ait kalıntıların araş-tırılması düşünülmüştür.

Av tüfeği ile değişik mesafeler-den kuzu karaciğerine ve kirece deneme atışları yapılarak, her atış sonrasında silah üzerinde hedefe ait kalıntı araştırılmıştır. Karaciğere yapılan atışlardan sonra silah üzerindeki biyolojik kalıntıları araştırmak amacıy-la yeni bir Luminol türevi olan Bluestar isimli ticari kit kulla-nılmıştır.

Karaciğere yapılan atışlarda he-defe 60 cm mesafe içinden olan-larda av tüfeği namlusu içinde, 30 cm mesafe içinden olanlar-

da namlu üzerinde kan lekele-ri tespit edildi. Kirece yapılan atışlarda ise 120 cm ve daha az mesafelerden yapılan atışlar-da namlu içinde kireç saptandı. Kireç damlacıklarının namlu üzerine sıçraması ise ancak 100 cm ve daha az mesafelerden ya-pılan atışlarda görüldü. Bu ne-denle silah üzerinde hedefe ait kalıntıların araştırılması, rutin balistik araştırmanın bir parçası olmalıdır.

Anahtar kelimeler: av tüfeği, kan lekesi, Luminol

38Adli Tıp Dergisi / Turkish Journal of Forensic Medicine, Cilt / Vol.:24, Sayı / No:3


INTRODUCTION

In criminal cases, the detection of gunshot residues around the bullet entrance hole provides information about the shot dis-tance. The marks on the cartrid-ge cases and bullets are exami-ned to determine the firearm, by which the shot is fired. The con-sistency between the bullets ob-tained from the wound area and the marks on the bullets obtai-ned from the test shots provide evidence that may clarify whet-her the wound is inflicted by a particular weapon.

However, it is harder to solve a crime if the bullet leaves the body. Even if a suspected fire-arm or even a bullet or cartridge case is found in the crime sce-ne, the debates may still conti-nue. The following question still persists: May this bullet have no connection with the crime? Especially, when multiple sus-pects and suspected firearms are present, the suspicion can not be ruled out. On the other hand, wounds inflicted by shot-guns are particularly challen-ging. Because, even if pellets are obtained from the body, they do not provide characteristic information about the firearm, which sent them to the target. In such circumstances, detection of residues belonging to the tar-get may shed light on a lawsuit. As the bullets or pellets strike a live target, some of the blood and pieces of tissue that ejects from the target may reach the firearm. This is called backspat-ter. Backspatter is defined as

the ejection of blood or tissue pieces from a gunshot entran-ce wound against the line of fire (1-4). The presence of blood in the barrel is a well-known phe-nomenon. The blood detected in the barrel is considered as an indicator of suicide due to an contact shot. In a study investi-gating 195 suicide cases, blood was detected in the barrel in 63% and on the muzzle in 86% of the cases (5). In the same study, an additional 202 suicide cases were investigated. In the next group of cases, the presence of blood was investigated by using a different chemical and blood in the barrel and on the muzzle was determined in 48% and 66% of the cases, respectively.

It has been reported that the detection of blood in the barrel indicates that the gun was only a few inches away from the body when the shot was fired (1b). However, backspatter may be seen not only in contact shots but also in shots fired from long distances. The present study aims to determine the distan-ces, in which the presence of backspatter should be anticipa-ted.

In order to demonstrate the presence of blood stains in and on the barrel, the use of a pre-sumptive blood test was envi-saged. Luminol (5-amino-2,3-dihydrophthalazine-1,4 dione) is the most popular of presump-tive blood tests. The oxidation of Luminol results in chemilu-minescence. In the presence of an oxidant, transition metal

cations catalyze the oxidation of Luminol. Hemoglobin, which transports Fe+ ions and has an activity resembling that of pe-roxidase, demonstrates this catalyzer effect. Thus, blood catalyzes the oxidation reaction between Luminol and H2O2. As a result of the oxidation, the exi-tated form of Luminol produces a blue-coloured luminescence (6,7).

It has been reported that Lumi-nol has the highest sensitivity and specificity compared to the other blood stain tests (8, 9) and does not have a negative effect on PCR steps (6, 9). Another ad-vantage of Luminol is that its to-xic or carcinogenic effect could not be demonstrated until today (10).

MATERIAL AND METHOD

After firing test shots from diffe-rent distances, residues belon-ging to the target were investi-gated on the firearm. A 12 gauge single barrel shotgun was used as the study’s firearm, along with 28 g number 6 shots. The test shots were fired on open ground and on a soft soil surfa-ce. When the target was below, the shots were invariably fired from the top with an angle of 45 degrees. After the shots, the in-terior and exterior of the barrel were examined in a luminous environment and their photog-raphs were taken. Smear was taken from the barrel’s interior after each shot. For this purpo-


se, a ball shaped piece of cloth that could fit into the barrel was tied to the end of a stick. Follo-wing each shot, a piece of paper was placed in front of the hole from which the empty cartridge case was retrieved. The paper was pushed into the barrel with the stick and taken out from the front edge of the muzzle. This procedure was applied only once. In this way, smear was obtained from inside of the bar-rel. The papers were examined for stains. After each shot, an additional shot was fired at the empty ground and the barrel’s interior was cleaned.

Shots fired at biological samp-les: Lamb livers purchased from a market were used as targets. The livers wrapped in nylon bags were placed on the inclined soil ground. Shots were fired from different distances. Initially, 5 shots were fired at the soil ground with no biolo-gical materials in target. Then 5 shots were fired from each of the 5 different distances, which were designated as 120, 60, 30,

15 and 7.5 centimeters between the muzzle and the target. Af-ter the shots, pages of a squa-red notebook, which measured 10,5x15 cm, were used to take smears.

In order to make the little blo-od stains visible, a commercial kit named Bluestar was used. The kit including Luminol was prepared in accordance with the prospectus (6). The prepa-red spray was applied to the paper and the barrel’s interior and exterior to detect the blood stains.

Shots fired at the lime pit: A hole measuring 25x25x25 cm was dug on the soft soil. Then the hole was filled with melted lime. The density of the lime re-sembled that of yoghurt. In the beginning, 5 shots were fired at the soil ground without the pre-sence of lime in order to form a control group. 12 shot distan-ces ranging between 120 and 10 cm were envisaged. There would be 10 centimeters bet-ween each distance and 5 shots

would be fired from each point. After shots were fired from dis-tances of 120 cm, 110 cm, 100 cm, 90 cm, 80 cm and 70 cm, with 5 shots fired from each dis-tance, it was observed that the shots planned to be fired from a distance less than 70 centi-meters would make the study difficult to continue because a large amount of lime was being spattered on the shooter’s face. Thus, the study was concluded since it was thought that the purpose of the study had been achieved. After the shots; soft, dark blue napkin papers mea-suring 10x10 cm were used to take smears from inside the barrel. White lime marks were sought on the obtained smears.

The observations were photog-raphed with a Sony DSC W35 amateur camera. During the photoshoot; the camera was placed on a tripod, the auto-matic shutter release was set to 2 seconds and ISO mode and macro mode were used for pho-tographing without flashlight and for close-ups, respectively.

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Fig 1. The stains with no backspatter were black and homogeneous.

Fig 2. The black stains on the paper obtained after the shots fired from a distance of 60 cm or less had brown-pink stains on them. Arrows show brown-pink stains.



RESULTS

Shots fired at lamb livers: Af-ter the shots, Luminol was used for the detection of blood stains. No luminescence was observed even when distinctive marks were present on the barrel. It was tho-ught that this resulted from the insufficient darkening of the en-vironment. Accordingly, the Lu-minol application to the smears obtained from inside of the barrel was postponed. Butterfly-shaped stains were formed on the sme-ars obtained from inside of the barrel. The colour of the stains on the smears that were obtai-ned from the barrel’s interior was

pale brown before the shots whi-le it was observed that it turned black after the shots. The stains obtained after the shots fired at the soil with no biological mate-rial in target were homogeneous (Figure 1). Similarly, the stains obtained after the test shots fired at the livers from a distance of 120 cm were black and homoge-neous. However, the black stains on the paper obtained after the shots fired from a distance of 60 cm or less had brown-pink stains on them, which did not exceed 1-2 mm (Figure 2). Surprisingly, the-re was no increase in the number and dimension of these stains in spite of the decrease in distance.

Backspatter was not observed in the shots fired from 60 cm away from the target. However, litt-le stains spattered on the bar-rel were observed after the test shots fired from a distance of 30 cm or less (Figure 3). As the sta-ins were carefully examined, it was seen that they were not blo-od stains but tissue pieces with a diameter of 1-2 mm. The back-spatter results of the 25 shots fi-red at the livers according to the shooting distances are presented in Table 1.

A few days after the smears were obtained; 125 ml of spray was prepared using Bluestar kit once

Distances

(cm)

Backspatter’s localization

Shots with no backspatter (-)

Shots with backspatter (+)

Total shots

120 barrel’s interior barrel’s exterior

5

5

0

0

5

5


3

5

2

0

5

5


0

0

5

5

5

5


0

0

5

5

5

5

7,5 barrel’s interior barrel’s exterior

0

0

5

5

5

5

Total barrel’s interior barrel’s exterior

8

10

17

15

25

25

Table-1. The backspatter results of the 25 shots fired at the livers according to the shooting distances


again. In a room without windows, Luminol was applied to the pa-pers. Luminescence was not ob-served on the piece of paper, with which smear stains were received from the barrel’s exterior. On the other hand, luminescence was observed on all the smear samp-les received from the barrel’s in-terior. On all the papers, including those used before the shots, lar-ge, homogenous and weak blue luminescence, which was con-sistent with the butterfly-shaped stain patterns, was obtained. On the other hand, when Luminol was applied to the papers that were used during the shots fired from a distance of 60 cm or less, more distinctive luminescence areas with a diameter of 1-2 mm were detected inside the pale blue lu-minescence. These luminescence areas were in perfect consistency with the localities where pink-brown coloured small stains were present. This luminescence was brighter than the luminescen-ce observed on the butterfly-like

stains. However, perfect darkro-om conditions were needed for the observation. An attempt to photograph these luminescence areas was made. However, this attempt was unsuccessful.

Of the 25 test shots fired at the livers, backspatter was observed in the barrel in 17 and outside the barrel in 15 shots. The differen-ce was not statistically significant (Pearson’s chi-square: 0.347, p=0.556).

The shots fired at the lime pit: As the smear samples, which were received from the barrel’s interior with a piece of paper, were exa-mined starting from the first sho-oting distance of 120 cm, it was observed that lime stains were present on some of the papers (Figure 4). In the test shots fired from 80 cm and less, lime stains on the paper are clear (Figure 5). In the test shots fired from 120 cm and 110 cm, no stains were observed on the outer surface of

the barrel. In all the 5 test shots fired from 100 cm, white stains were present inside the barrel. Beginning from this distance, few stains began to be observed on the barrel. Following this distan-ce, an increase in the stains was observed in the 5 shots fired from each of the shooting distances of 90 cm, 80 cm and 70 cm. (Figu-re 6 and 7) In the first shot fired from 60 cm, a large amount of lime spattered on the barrel’s in-terior and exterior and on the face of the study assistant (Figure 8). Thinking that the purpose was ac-hieved, the study was concluded. The backspatter results of the 31 shots fired at the lime according to the shooting distances are pre-sented in Table 2.

Of the 31 shots fired at the lime, backspatter was observed insi-de the barrel in 27 and outside the barrel in 19 shots. The dif-ference was statistically signi-ficant (Pearson’s chi-square: 5.391, p: 0.020)

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Fig 3. A piece of tissue with a diameter of 1-2 mm on the barrel.

Fig 4. The black stains on the paper obtained after the shots fired from a distance of 120 cm had white stains on them. Arrows show white stains.


DISCUSSION

Karger et al. defined back-spatters in two groups: Mic-robackspatter < 0.5 mm and makrobackspatter > 0.5 mm (2,3). They have reported that there is no correlation between the dimension of the particle and the distance traveled by it but small particles can not travel far away from the entrance hole because of the air resistance (3). This outcome was observed in our study too. Especially in the shots fired at the lime pit, lime particles measuring between 5 mm and a few centimeters in diameter were ejected meters away from the target. Numero-us stains were observed on the

camera, the tripod and the clot-hes of the researcher and the shooter (Figure 5). Thus, in an incident of crime, blood stains should be sought on the sus-pect and the suspected firearm in the presumed crime scene. The presence of such stains in a certain place indicates that the place may be the exact cri-me scene and their presence on the clothes of the suspect(s) or on the suspected weapon(s) indicates that the suspect(s) or the weapon(s) were present in the crime scene. Certainly, the detection of these stains with pre-tests such as the Luminol method is not enough by itself. The next step should be using more precise methods such as

the use of antibodies specific for human blood to prove that the stain really contains human blo-od. A shorter method includes direct DNA amplification and acquisition of STR profiles after the pre-tests.

The suspected weapons sho-uld be the first to be examined for blood stains. Because the presence of blood stains on a firearm can prove that that particular firearm was used in a particular criminal incident. Certainly, the definitive conc-lusion can only be drawn when the DNA profile obtained from the stain is proved to be con-sistent with that of the wounded person. Additionally, the shape

Distances

(cm)Backspatter’s localization

Shots with no backspatter (-)

Shots with backspatter (+)

Total shots

120 barrel’s interior barrel’s exterior3

5

2

0

5

5


5

4

0

5

5


2

5

3

5

5


0

5

5

5

5


0

5

5

5

5


0

5

5

5

5


0

1

1

1

1

Total barrel’s interior barrel’s exterior4

12

27

19

31

31

Table-2. The backspatter results of the 31 shots fired at the lime according to the shooting distances



and distribution of the stains may provide information about the direction and distance of the shot. Even if bullets or cartrid-ge cases are obtained from the crime scene and they show si-milarities with those obtained from the test shots, the presen-ce of residues belonging to the target is still needed to support the diagnosis. In circumstances where shotguns are used, the presence of backspatter inside the barrel and on the outside of the weapon may provide the only exact proof. Therefore, the examination of the suspected firearms for stains should be-come a part of the routine in-vestigation. In circumstances where blood can not be seen macroscopically, appropriate lightening, magnification and chemical tests are proposed. The determination of the pre-sence of blood inside the barrel and the determination of the DNA profile by using that blood provide crucial proofs in solving

a crime. It has been reported that blood can be obtained even if additional shots are fired after it is spattered into the barrel of the firearm (1b).

Theoretically, the probability of a spatter of a blood droplet or tissue piece on the barrel sho-uld not be different from that of the spatter of other objects located at an identical distance because the size of the outer and inner surfaces of the barrel is approximately identical. Ho-wever, the barrel’s interior may be a better source for the in-vestigation of these stains. The probability of the accumulation of the spattered blood or tissue particles inside the barrel may be higher. Additionally, these particles may reach the barrel’s interior from longer distances compared to the barrel’s exte-rior, which was also shown by the present study. Positive re-sults were obtained inside the barrel in the shots fired from

60 cm or less and outside the barrel in the shots fired from 30 cm or less. This should have re-sulted from the fact that the ex-pansion in the barrel occurring due to the explosion is quickly followed by contraction. The hyper-expansion of the emer-ging gases causes a subsequ-ent contraction. This contrac-tion should be the mechanism behind the accumulation of the blood and tissue inside the bar-rel. Air resistance, which has been reported to constitute an obstacle to the travel of micro-backspatters to long distances, might play an opposite role in such circumstances.

According to the results of the tests carried out using livers, there was no statistical diffe-rence between the barrel’s in-terior and exterior in terms of backspatter. Since the blood stains were so difficult to dif-ferentiate from the dark colo-ured smut accumulated in the

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Fig 5. The white stains on the paper obtained after the shots fired from a distance of 80 cm.

Fig 6. Micro and macrobackspatter on the barrel.


barrel and the results obtained by Luminol were not distincti-ve enough, the experiment was repeated again using lime. The lime droplets were more visible in the black soot and this made the observation of the presence of backspatter much easier. The findings were consistent with those obtained in the shots fi-red at the livers. Certainly, the distances, number of shots and statistical interpretation of the results were different betwe-en the lime and liver tests. Ac-cording to the total number of shots, the backspatter rate in the barrel’s interior was found to be higher than the rate on the barrel’s exterior (p=0.020). This difference resulted from the long distances. Since the num-ber of shots was not enough, the statistical analysis of each distance could not be performed separately.

In both experiments, more sta-ins were observed in the barrel’s

interior than the barrel’s exteri-or in longer distances. However, a quantitative study to compare the density of the stains was not performed. Even so, the impression aroused in the lime experiment was that, as the dis-tance between the gun and the target decreased, the stains on the barrel became more dense compared to those in the barrel.

Backspatter was observed in the shots fired at livers from distances less than 60 cm. Ho-wever, the reason why these stains did not demonstrate an increase in shots performed at closer distances could not be clarified. A better understan-ding of the physical expansion and contraction characteristics of the firearm can help us find the answer of this question. Re-peating this study with different firearms may be beneficial. In this way, backspatter patterns can be determined according to different types of firearms and

different distances. Certainly, this requires more extensive studies performed under better conditions than this study.

Livers were used in the present study because we thought that the liver tissue contains a vast amount of blood. However, the-re was not as much blood in the livers as expected. Probably, most of the blood in the tissues was shed during the slaughte-ring. The remaining drippings should have left the tissue du-ring the period before and af-ter the purchase of the livers. As the stains spattered around from the livers were examined carefully (Figure 5), it was seen that they were not blood stains but tissue pieces measuring 1-2 mm in diameter. However, the author of the present study par-ticipated in hundreds of crime scene investigations, in which he had observed extensive blood stains spattered on the wall due to shots fired from shotguns.


Fig 7. Micro and macrobackspatter in the barrel.Fig 8. Massive lime backspatter on the barrel’s interior and exterior observed after the shots fired from a distance of 60 cm.


The test shots performed with the organs purchased from the market, however, could not rep-resent those scenes sufficiently. As for the shots performed with lime, backspatter was obser-ved to a great extent as expec-ted. The rate of backspatter in shots fired at live targets with a shotgun should be somewhere between the rates obtained in the lime and liver tests. Thus, it was thought that repeating this experiment using big research animals used for other purpo-ses or subjected to euthanasia might provide better supported results. Karger et al. performed a better study by using 9 live animals for the experiment (2-5). However, further studies are needed to investigate backspat-ter with different firearms and cartridges and in different com-binations of shooting distances.

Shotgun pellets do not contain characteristic information about the firearm, which sends them to the target. On the other hand, if the bullet leaves the body in injuries due to firearms with rifling grooves, the ambiguities are harder to resolve. In such circumstances, the biological residues in and on the barrel become the most important evi-dence of crime. At longer sho-oting distances, biological re-sidues may be observed more frequently in the barrel’s inte-rior compared to the barrel’s exterior. This was demonstrated by the experiment performed in the present study. Although the examination of the barrel’s inte-rior for blood stains seems to be a demanding task, it has its own advantages. The blood stains outside the barrel can be easily noticed and cleaned completely.

Additionally, during the defense of the suspect, it can be claimed that the presence of blood outsi-de the barrel is just a contami-nation. Hence, the detection of blood inside the barrel consti-tutes a more precious evidence.

As a result, it is likely to find blood stains related to back-spatter on the firearm and in-side the barrel. Depending on the type of the firearm, the type of the cartridge, shooting dis-tance, shooting angle and the characteristics of the body part, at which the shot is fired, back-spatter may be observed less or more or may not be observed at all. It is considerably difficult to predict in which cases it may be present. The firearms, which are suspected to be used in cri-minal incidents, should be rou-tinely examined for backspatter.

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