Analysis of beveling in gunshot entrance wounds

Forensic Science International 93 (1998) 45–60

Analysis of beveling in gunshot entrance wounds ´ Gerald Quatrehomme a , *, M. Yas¸ar ˚Is¸can b a

ˆ de Conf erences ´ ´ , Faculte´ de Medecine ´ ´ ´ de Nice, Laboratoire de Medecine Legale , Maıtre des Universites Avenue de Valombrose, 06107 Nice Cedex 2, France b 2727 NW 7 th Drive, Boca Raton, FL 33486, USA Received 12 May 1997; received in revised form 29 January 1998; accepted 2 February 1998

Abstract The analysis of skeletal trauma is an important aspect of forensic case work. Yet most major pathology references devote limited attention to this topic. The aim of this paper is to analyze beveling in gunshot entrance wounds, from a series of 27 cases with a total of 39 wounds. Assessment was made by measuring the external and internal cranial dimensions, describing the area of most pronounced beveling, and correlating the directions of the beveling with the trajectory of the bullet. Results indicated that inward beveling was found in 36 of 39 cases, the absence of beveling in four bones, and actual external beveling in one case. The inconsistency in the direction of most pronounced beveling in reference to the direction of shooting leads to the conclusion that this characteristic cannot be used to make a reliable assessment of the direction of fire.  1998 Elsevier Science Ireland Ltd. Keywords: Forensic anthropology; Bone; Gunshot wounds; Entry wounds; Beveling

1. Introduction Beveling in both entrance and exit gunshot wounds are well known to forensic pathologists [1–6]. Internal beveling is the classic hallmark of entrance wounds, and the shape of the beveling has been considered an indicator of the direction of fire and, to a certain extent, the type of weapon and caliber of the bullet [7–15]. However, a number of cases that do not follow this pattern have also been reported, including the absence of beveling [5,16], external beveling in keyhole defects produced by tangential shootings [17–19], external beveling of entrance wounds in perpendicular contact gunshots *Corresponding author. Tel.: 133 492 037763; fax: 133 492 038148; e-mail: [email protected] 0379-0738 / 98 / $19.00  1998 Elsevier Science Ireland Ltd. All rights reserved. PII S0379-0738( 98 )00030-9

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[17,20], and in shootings from a distance [17,21,22]. While there has been earlier work on beveling (e.g., Refs. [4,23,24]), there is no comparable study of this phenomenon based on a large, well-documented forensic skeletal series. Therefore, the aim of this work is to provide a comprehensive descriptive analysis of beveling in entrance wounds (occurrence, size, symmetrical or asymmetrical shape), and determine if the direction of the shot and its association with the prevalent direction of beveling can be made.

2. Materials and methods A forensic sample of 27 gunshot wound cases was studied. The sample was documented for trauma, age, sex, and race of the individuals, as well as the autopsy reports (including cause of death, photographs and crime scene investigation), although most cases did not have details of the specific weapons and ammunition responsible for the wounds. When the identity of the victim was unknown, age, race and sex were assessed using the usual anthropological methods [25]. These characteristics along with manner of death are summarized in Table 1. The manner of death is homicide in 23 out Table 1 Distribution of sample by age, sex, race, and manner of death Case no.

Sex

Race

Age

Manner of death

C1 C2 C3 C4 C5 C6 C7 a C8 C9 C10 a C11 a C12 C13 C14 a C15 C16 C17 C18 a C19 a C20 a C21 a C22 a C23 a,b C24 C25 a C26 a C27

Male Male Male Male Male Female Male Female Male Female Male Female Male Male Female Male Male Male Male Male Male Female Male Male Male Male Male

White White White White White White White White White White ‘Mixed‘ Black Black White White White White White White White White White Unknown White White Mixed White

41 45 47 28 50 19 50 18 53 20 20 14 47 30 20 20 27 45 45 28 40 30 Unknown 21 40 45 45

Suicide Homicide Suicide Homicide Homicide Homicide Homicide Homicide Homicide Homicide Homicide Homicide Homicide Homicide Homicide Homicide Homicide Homicide Homicide Homicide Homicide Homicide Unknown Homicide Homicide Homicide Suicide

a

Unknown remains; only the average of estimated age is indicated. Portion of calvarium only.

b

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of 27 cases—the rest include three suicides and one that could not be established from the remains. The shape, location, and size of each entrance wound were described with special focus on beveling. In each case, beveling was assessed in terms of its presence or absence, and what aspect of the bone it affected (ectocranial or endocranial). Beveling was quantified by comparing the surface area (in cm 2 ) of the external (ectocranial) opening made by the projectile with that of the internal (endocranial) defect including beveling. Then the ratio of external to internal dimensions was calculated to quantify the magnitude of the beveled area. Symmetrical beveling is that which is evenly distributed around the wound. Asymmetric beveling was diagnosed when one side of the hole was more pronounced. To analyze the latter, the skull was rotated from a standard anatomic position until the wound was perpendicular to the viewer, then the area of most pronounced beveling was recorded in clockwise fashion, giving a simple two-dimensional assessment (e.g., 2 to 4 o’clock). A Pearson correlation was carried out to evaluate the relationship between the surface areas of the holes and magnitude of beveling. A three-dimensional assessment of the direction of beveling (angulation) was made with a knitting needle held tangentially to the most pronounced area of beveling. This was described as downward, leftward, etc. The trajectory of shooting was assessed by measuring angles in reference to either a sagittal or coronal plane and the Frankfort horizontal. When available, autopsy findings were used to aid this assessment. Finally, the direction of beveling was compared with the direction of the shot. When beveling predicts the exact direction and angle of the projectile, this is referred to as a positive correlation. When only one of these parameters is predicted, this is considered a partial correlation. If beveling predicts neither, then there is no correlation.

3. Results Of the 27 cases included in the study, there were 39 entry wounds. Table 2 shows the location and shape of the wounds, as well as the presence and symmetry of internal beveling. Most entry wounds are round, yet exhibit asymmetrical internal beveling. Beveling is symmetrical or nearly so in only six cases, and appears to be independent of the irregularity of the wound. For each case, the surface area of most pronounced beveling as well as the external and internal dimensions of the entry wounds are listed in Table 3. This table also contains the ratios quantifying the proportional increase in size due to beveling. For example, in C1 the external (ectocranial) dimension was 0.78 cm 2 and internal (endocranial) dimension was 1.12 cm 2 , giving a ratio of 1.43 (1.12 / 0.78). This indicates that the endocranial hole plus the beveled area is 1.43 times larger than the external opening. The ratio ranges from 1.04 to 7.70, and a ratio of 1.00 indicates that there is no beveling. The largest increase was seen in a right temporal bone (6.41 in C26) and clavicle (7.70 in C14). There are only four cases without internal beveling. These are in the left temporal (C11), maxilla (C11), internal wall of the orbit (C11) and left occipital bone (C14). Beveling is roughly measured as the area between the hour and minute hands of a clock. The greatest coverage was seen in a left parietal (11 hours) in C2 followed by a temporal bone (9 hours) in C9. Table 4 shows the results of the

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Table 2 Location and shape of the wounds and presence or absence of symmetrical or asymmetrical internal beveling Case no.

Location

Shape of wound

Internal beveling

Symmetrical / asymmetrical

C1 C2 C3 C4 C5

Right temporal L. posterior parietal R. fronto-parieto-temporal Right frontal Left parietal Left occipital Left coronal suture Right parietal vertex Right occipital Right occipital Posterior right mastoid Left temporal Left occipital Left temporal L. zygomatic. proc.

Round Very irregular Oval, irregular Round Ovoid, and square Round Round Round Round Oval Triangle Round, irregular Triangle Oval, irregular Oval

Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes No Yes

Asymmetrical Nearly symmetrical Asymmetrical Asymmetrical Asymmetrical Asymmetrical Asymmetrical Asymmetrical Asymmetrical Symmetrical Symmetrical Asymmetrical Asymmetrical

Internal L. orbit External orbit edge Parietal Left frontal R. post. parietal Left frontal

Square, irregular Semilunar Bullet-shape Oval Oval Round, oval (Depressed fracture) Oval Semilunar Triangle Semilunar Oval a Round Oval a Round Oval

Yes Yes Yes Yes Yes

Asymmetrical (tangential shot) No Asymmetrical Asymmetrical Asymmetrical Asymmetrical Asymmetrical

No Yes Yes Yes Yes Yes Yes Yes Yes

Asymmetrical Asymmetrical Symmetrical Asymmetrical Asymmetrical Asymmetrical Asymmetrical Symmetrical

Round Oval Oval Oval Round Triangle Oval Round Oval, irregular Oval Round, irregular Oval Round, irregular

Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes

Asymmetrical Asymmetrical Asymmetrical Asymmetrical Asymmetrical Asymmetrical Asymmetrical Symmetrical Asymmetrical Asymmetrical Asymmetrical Asymmetrical Asymmetrical

C6 C7 C8 C9 C10 C11

C12 C13

C14 C15

C16

C17 C18 C19 C20 C21 C22 C23 C24 C25 C26 C27 a

Left occipital Left clavicle Left occipital Left mandible notch Atlas L. mand. ramus R. mand. ramus Left rib Left occipital Depressed fracture Right temporal Right occipital Left parietal L. post. parietal Left parietal Right occipital Right temporal Right parietal Right frontal Left parietal L. temporo-occipital Right temporal Right temporal

Tangential shot.

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Table 3 Location of the wounds, areas of most pronounced beveling (clockwise), internal (Int) and external (Ext) wound surface size (in cm 2 ) and their ratio Case no.

Location

Ext size

Int size

Int / Ext ratio

Most beveled area (clockwise)

C1 C2 C3 C4 C5

Right temporal L. post. parietal Right fronto-parieto-temp a Right frontal Left parietal Left occipital a Left coronal suture R. parietal vertex Right occipital Right occipital Posterior to right mastoid Left temporal Left occipital Left temporal L. orbit int. wall Left parietal Left frontal R. post. parietal L. frontal c L. frontal c Left occipital Left clavicle Left occipital L. mand. notch L. mand. ramus Left rib Left occipital Right temporal Right occipital Left parietal L. post. parietal Left parietal Right occipital Right temporal Right parietal Right frontal Left parietal Left temporo-occipital Right temporal Right temporal

0.78 1.13 1.18 3.14 1.49 4.91 0.20 0.26 0.78 2.12 0.80 0.28 0.75 0.88 2.35 0.76 0.75 1.26 1.04 0.38 1.21 0.20 0.33 0.20 0.38 0.78 1.41 0.50 0.63 0.94 1.04 1.77 0.32 2.40 1.13 1.63 1.41 0.63 0.49 0.78

1.12 3.92 1.71 4.91 3.53 5.72 0.38 1.18 1.54 2.38 2.67 0.38 0.78 0.94 2.35 1.79 1.53 2.98

1.43 3.47 1.45 1.56 2.37 1.17 1.90 4.54 1.97 1.12 3.34 1.36 1.04 1.07 1.00 2.36 2.04 2.37

2.35 1.21 1.54 0.82 0.28 0.78 0.93 1.65 0.78 1.04 1.41 1.65 2.35 0.95 2.98 2.00 2.64 3.11 2.83 3.14 1.77

6.18 1.00 7.70 2.48 1.40 2.05 1.19 1.17 1.56 1.65 1.50 1.59 1.33 2.97 1.24 1.77 1.62 2.21 4.49 6.41 2.27

2 to 8 12 to 11 2 to 7 9 to 3 12 to 12 9 to 4 8 to 10 9 to 12 Visible wound b Visible wound b 12 to 12 7 to 4 12 to 6 6 to 11 7 to 12 12 to 6 2 to 9 6 to 10 Depressed fracture 12 to 6 No beveling Visible wound d 10 to 2 Visible wound a,d 5 to 10 Visible wound d 12 to 12 8 to 12 4 to 6 6 to 8 4 to 9 9 to 12 4 to 8 3 to 5 12 to 12 8 to 11 and 2 to 5 9 to 12 7 to 9 6 to 10 3 to 6

C6 C7 C8 C9 C10 C11 C12 C13

C14 C15 C16 C17 C18 C19 C20 C21 C22 C23 C24 C25 C26 C27 a

Incomplete semilunar shape wounds. Because of missing bones, only part of the wound is visible. c These two lesions were created by the same tangential shot causing a depressed fracture with no penetration, and an entrance hole. d Tangential shot. b

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Table 4 Pearson correlation analysis of the surface areas of bullet holes and clockwise coverage Variables

Ectocranial surface area

Endocranial surface area

Endocranial / ectocranial ratio

Endocranial surface area Endocranial / Ectocranial ratio Clockwise coverage

0.78 a 20.38 b 0.10

0.13 0.09

20.01

a

Statistically significant at P,0.001 level. Statistically significant at P,0.05 level.

b

correlation analysis using the data in Table 3. It is clear that both external and internal surface areas of defect sizes are significantly correlated. But there was no association between the amount of beveling and the size of the entry defect. Table 5 shows the frequency of occurrence of external beveling in entry wounds, as well as the presence of small external lesions at the edges of the external wounds. In the 10 cases where such features are seen, only one displays external beveling (C19). The other shows only small cortical lesions of the edges (pseudo-outward beveling). In all these cases the diagnosis of entrance wound, however, cannot be confused because of the consistent presence of the expected internal beveling. Table 6 indicates the direction of beveling in comparison with the direction of the shooting. It is apparent that these two variables are the same in five cases, and partially correlated in eight. However, there is no correlation in 10 cases. This correlation could not be made in 16 cases, because the precise direction of the shot was unknown. All wounds were not only quantified, but also analyzed for shape and location. In C1 (right temporal), C12 (parietal), and C23 (vault including lambda) the direction of shooting is unknown because there are only small pieces of bone. Frontal entrance wounds were seen in cases C4, C13, and C24. In C24 the gunshot wound perforated the frontal sinus. Parietal entrances are recorded in C2, C5, C12, C13, C19, C20, C23, and C24, temporal entrances in C1, C8, C9, C11, C18, C22, C26, and C27, and occipital entries in C6, C10, C14, C15, C17, C18, and C21. Some wounds are on the sutures: right fronto-parieto-temporal junction (C3), left coronal suture 11 cm away from bregma Table 5 External beveling and lesions associated with entrance wounds and associated internal beveling Case no.

Location

Associated int. beveling

External lesion size

C2 C4 C6

L. posterior parietal Right frontal Left temporal Right parietal Right occipital Posterior to right mastoid Left temporal Occipital Right temporal Left parietal Left parietal

Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes

Two 1-mm lesions Very small Very small 1 mm 132 mm 0.5 mm 0.131 Very small Very small Outward beveling Very small

C7 C8 C9 C17 C18 C19 C24

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Table 6 Correlation between beveling and direction of shooting Case

Direction of beveling a

Direction of shooting

Correlation

C1 C2 C3 b

Downward Nearly symmetrical Backward Downward Backward Upward Left parietal Upward Left occipital a Upward, leftward Left temporal Backward Right parietal vertex Backward, leftward Right occipital Symmetrical Right occipital Leftward Upward Symmetrical Upward, backward Leftward Left temporal Downward, backward Edge of the orbit Upward, backward Forward Left frontal Rightward, downward R. posterior parietal Forward, downward, rightward Left frontal coronal Forward, Upward Left clavicle Backward Left occipital Upward Left mandible Semilunar wound Atlas No beveling L. mandibular ramus Downward, backward Left rib Backward, rightward T7 Backward, rightward Symmetrical Rightward, upward, forward

Unknown Unknown 208 coronal, 308 Frankfort Leftward, upward, backward 208 coronal, 308 Frankfort Leftward, downward, backward 208 sagittal, 158 Frankfort Rightward, downward, forward

Unknown Unknown None

Rightward, upward, forward 458 sagittal, 108 Frankfort Rightward, upward, backward Rightward Downward, forward

Partial Partial

Unknown

Unknown

Unknown

Unknown

Unknown Transverse, rightward Unknown 808 sagittal, 108 Frankfort Upward, rightward, forward 108 coronal, 308 Frankfort Rightward, upward, backward Unknown

Unknown None Unknown

Excellent Unknown

Unknown

Unknown

Unknown 108 coronal, 08 Frankfort Forward, horizontal, rightward

Unknown

Backward

Excellent

Unknown

Unknown

Unknown

Unknown

C4 b,c C5 c

C6

C7

C8 C9 c,d C10 d C11

C12 C13

C14 e C15

C16

C17 b

None

None

None

None

Partial

Tangential Downward, backward Backward Other directions unknown

Excellent Unknown

Rightward 308 sagittal, 58 Frankfort

Excellent Unknown

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Table 6. Continued Case

Direction of beveling a

Direction of shooting

Correlation

C18

Right temporal Upward Right occipital Downward, leftward Left parietal d Downward, backward Left posterior parietal f Downward, backward Upward, backward Downward Downward, backward Leftward, upward, backward Symmetrical Right frontal, frontal sinus Left parietal Backward, upward

308 coronal, 58 Frankfort Upward, backward, leftward 458 sagittal, 08 Frankfort Leftward, horizontal, forward

Partial

Forward, rightward, upward

None

Horizontal, rightward Forward, upward, rightward Unknown 458 coronal, 158 Frankfort

None Partial Unknown Partial

Unknown Unknown

Unknown Unknown

Forward, downward 108 sagittal, 808 Frankfort Upward, forward 458 sagittal, 58 Frankfort 808 sagittal, 08 Frankfort Forward, leftward, horizontal 308 coronal, 08 Frankfort Backward, leftward, horizontal

None

C19

C20 C21 C22 C23 C24

C25

Backward, Downward

C26

Downward Forward Downward Backward

C27

Excellent

None Partial Partial

a

When there is only one shot, location of the wound is noted in Table 2. Only part of the wound is visible. c Direction is estimated from the autopsy and / or X-rays. d Skull in multiple pieces was glued before analysis. e Semilunar wound. f Outward beveling forward and downward. b

(C6), left temporo-occipital near the junction of the parieto-mastoid and occipitomastoid sutures (C25), and at the junction of lambdoid, squamosal, and occipital sutures (C8). One entry is associated with a wormian bone, but it was not dislodged (C13). The other entrance wounds are in the left zygomatic process (C11), the internal wall of left orbit (C11), the external orbit edge (C11), the mandibular notch (C15) and ramus (C16). Most entrances are of classic round or ovoid shape (C13, Fig. 1A), but others include a rectangle with rounded corners in the left parietal (C5, C24), an irregular square in the internal wall of the left orbit (C11), a triangle in the left occipital (C10, C15), and the right occipital (C21), an irregular diamond in the left posterior parietal (C2), and ‘bullet’ shaped in a right parietal (C12, Fig. 1C). Irregular entries appear in the frontal (C24), temporal (C9, C11, C27), left posterior parietal (C2, Fig. 2A), right fronto-parietotemporal junction (C3), and left temporo-occipital bones (C25). There is a pseudo-keyhole entrance in the right occipital (C7) posterior to the foramen magnum (C7), and consists of two connecting entry wounds. Depressed fractures are seen in the left frontal near bregma (C13, Fig. 2C) and in the left occipital bone (C17). Sometimes there is only a semilunar shape, as in C3 and C4. The skull C10 was found in

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Fig. 1. Typical ovoid entrance hole in left frontal bone (C13). Sharp-edged, punched-out, clean appearance of the external wound in (A). Asymmetry of internal beveling in (B). C12 shows odd bullet-shaped entry wound in parietal. External surface in (C). Asymmetry of beveling in (D) (internal surface).

numerous pieces and had to be glued prior to analysis. A circular fracture surrounds the entrance wound in the right temporal bone (C22). There were a few postcranial remains available to analyze. These include a left clavicle (C14), atlas (C15) and left rib (C16). Tangential oval wounds were observed in several cases and depressed fractures in the left frontal (C13) and the left occipital (C17), left zygomatic process (C11), external orbit edge (C11, Fig. 3A), atlas (C15), and right mandible (C16). Most of the cases display asymmetrical internal beveling (C13, Fig. 1B), except for wounds in the left posterior parietal (C2, Fig. 2B), right occipital (C7), posterior to right mastoid (C8), left mandible (C15, Fig. 3D), left occipital (C17), and right parietal (C23) (see Table 2). It should be noted that, as in C15, asymmetry cannot be assessed in semilunar defects (Fig. 3C) when the wound occurs at the edge of the bone, as well as in those cases where part of the bone is missing. Symmetry is linked with a very irregular entrance wound in the left parietal (C2), a triangular shape in the right temporal (C8), a semilunar round defect in the mandibular notch (C15), a round-shape in right parietal

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Fig. 2. Irregular entry wound in left posterior parietal (C2). External surface in (A). A rough symmetry of the beveling on the internal surface in (B), despite the irregularity of the wound. Tangential gunshot wound in (C) showing depressed fracture in left frontal. External surface in (C) and internal in (D). Direction of shot (upward, slightly on the left on the picture) can be deduced both from external and internal surfaces.

(C23), and the occipital (C7). Symmetrical beveling is also seen in an ovoid depressed fracture of the left occipital (C17). Asymmetry is linked with round or ovoid entrances in frontal (C4, C13) (Fig. 1B), right temporal (C1, C18), left parietal (C20), left occipital (C5), left fronto-parietal (C6) bones, left mandibular ramus (C16), and left rib (C16). It is connected with a semilunar defect in the external orbit edge (C11, Fig. 3A), and left clavicle (C14). It was seen with a round but irregular entry in the left temporo-occipital (C25), and the right temporal (C27). Asymmetry is also associated with oval entrance wounds in the left frontal (C13), the parietal (C19), the posterior parietal (C13, C19), the occipital (C14, C18) and right temporal (C22, C26). As is the

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Fig. 3. Tangential gunshot wound striking the external right orbit margin (C11), with punched out appearance internally and beveling externally in (A). Direction of shooting is from right to left. (B) (C24) shows butterfly-shape entry wound in internal surface of frontal sinus. Beveling occurs on thick regions of bones and is absent on thin parts. (C) Tangential gunshot wound with semilunar defect in mandible displaying clean and punched-out appearance of external surface. There is symmetrical beveling (internal surface) in (D). Direction of the shot is from lateral to medial.

case with an irregular oval in the left temporal (C11), right frontal (C24), and right fronto-parieto-temporal junction (C3). The other cases of asymmetry are in a roughly oval-square shape in the left parietal (C24), a triangle shape in the occipital (C10, C15, C21) and an unusual ‘bullet-shape’ (C12, Fig. 1D).

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4. Discussion Endocranial beveling is one of the most important indicators of an entry wound to the skull. Classic entrance wounds are round or ovoid-shaped openings with sharp edges and a clear punched-out appearance. In certain cases, internal beveling can be very useful to identify an entrance wound, as, for example, when it displays an unusual shape (Fig. 1C,D), is very irregular (Fig. 2A,B) and could be confused with an exit wound, or when the skull is extremely fragmented (e.g., case C10). Furthermore, other kinds of beveling were also observed elsewhere, e.g., left clavicle (C14), ribs (C16), vertebrae (atlas, C15), orbital margins (C11, Fig. 3A), zygomatic process (C11), and mandibular ramus (C16). This beveling is also noted in the sternum and iliac crest in the literature [13]. As anticipated, the external entrance hole surface area is significantly correlated with the internal surface area of the defect. However, the size of the surface area did not show any association with the size of the most beveled area, suggesting that areas damaged by the bullet may not have any relationship to the size of the entrance hole. Tamaska’s [9] tests showed that an entrance hole might even be slightly smaller than the projectile because of the elasticity of living bone. Pollak and Ritt [13] reported similar findings in the postcranial skeleton with fully jacketed 7.65 mm caliber bullet, while .22s produce larger defects than the bullet. Thus, a particular bullet cannot be conclusively ruled out on that basis. There was no beveling in only four skeletal components, and in all cases the affected area was relatively thin. As noted by DiMaio [5] there is no beveling when the bone is too thin and the creation of the inverted funnel-shaped wound tract is not possible, as in orbital plates or the temporal bone. This suggests that a minimum bone thickness is necessary. An example of this is specimen C24 where the bullet struck and perforated the frontal sinus (Fig. 3B): beveling occurred only in the thick parts of bone, on the right and left; but was absent where the bone was very thin, resulting in a butterfly shape. In this series there was no beveling in ribs and vertebrae, where the shot was tangential. External beveling of an entrance wound is an important phenomenon because it may be mistaken for an exit wound [17,19,22,26,27]. Coe [17] claimed that this effect is ‘‘almost routinely seen in high-velocity bullet wounds of the head, and is common in handgun wounds as well, although minor in degree and not completely around the perforation of the bone’’. Nevertheless, true ectocranial beveling of entrance wound was very rare in this series—only one case (left parietal bone: C19, Fig. 4A). External beveling in a perpendicular shooting may indicate a contact wound from a handgun. Coe [17] collected a few examples, including a case where a .38 caliber handgun shot to the occiput resulted in a partially circumferential external beveling of the entrance wound resembling a keyhole defect. In another case with a .22, there was complete circumferential external beveling in the forehead, and an almost intact bullet was recovered from the occipital area. The same author reported a case involving a .32 caliber semi-automatic pistol wound to the head, with complete circumferential beveling of the entrance: the bullet was recovered from the occipital lobe of the brain. In rare cases this may occur when the shot is fired from a distance: Peterson [22] reported a perforating gunshot wound of the head with a standard fully jacketed 5.56-mm (.223 caliber) ‘military ball’ of the M8-85 (62-grain) type from a distance of 4 feet (1.2 m), perpendicular to the

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Fig. 4. Case C19 shows rare external beveling of an entry wound in left parietal bone in (A). Pseudo-outward beveling with little erosions and minimal fractures of edges of left parietal (external surface) in (B). (C,D) The area with most pronounced beveling can point opposite to the direction of fire, which is from left to right in (D).

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head; striking the right parietal bone above the right external auditory meatus. The entrance defect was 5.5 mm in diameter, surrounded by a symmetrical 2.0 mm margin of external beveling. There was also internal beveling on the inner table. Baik and associates [21] reported a case of external beveling of an entry wound made by a .22 caliber rifle bullet which entered the frontal bone, in the midline, 2.5 cm from the vertex with no evidence of close-range firing on the scalp. When the bullet strikes the skull perpendicularly to the surface of the bone, external beveling may be partially or completely circumferential [17]. Such incomplete circumferential beveling may produce a defect resembling a keyhole lesion and suggests a tangential wound (see Ref. [28]). There is no clear explanation for this rarity. It may be due to the chipping of the outer layer of the bone around the defect, produced by the forceful return of gases through the bullet hole in contact shots of head [7]. Some authors attribute it to the rotary motion of the bullet [7,21]. But this mechanism seems almost impossible, because the bullet only makes a portion of a turn while penetrating the bone. Another explanation is that in shots fired from a distance, the release of kinetic energy within the skull produces backward explosive pressure through the entrance wound, but this does not seem plausible when a small-caliber, low-velocity bullet is involved [17,22]. For Peterson [22] the blowback from pressure associated with temporary cavity formation is the most likely explanation of the external beveling. Baik et al. [21] think that there is probably a combination of several factors including the angle of the shot, the twisting force of the rotating bullet, the blow-back effect, the velocity, shape and size of the bullet, the outspread of the kinetic energy from the bullet and the resistance of the skull. It should further be noted that internal beveling of exit wounds is also extremely rare [27]. External beveling is also described in keyhole defects. These are composed of a circular or ovoid entrance with internal beveling, and a triangular or ovoid exit portion with external beveling. One portion of the bullet enters the cranial vault while the second part is deflected outward, exiting the bone almost immediately after penetration. These keyhole entries are seen in tangential shootings [16,18,24,29], and when the skin is present, it shows typical grazing indicating the direction of fire. Moreover, Frazer [20] stated that there may be a keyhole defect with both external and internal beveling around one hole when two bullets were fired in contact with the skull. In general, keyhole defects are rarely reported in the literature [7,16,17,20,29]. Pseudo-outward beveling is commonly seen surrounding the ectocranial aspect of the entrance wound. This defect is usually described as little erosions or minimal fractures at the edges of the wound. It was encountered in nine cases, e.g., C24 (Fig. 4B). This could be explained as chips of bone that have flaked off the edge of the entry defect producing an effect resembling a beveling and is very superficial in all cases [5,7]. In tangential gunshot wounds, the line of fire can be established from the ectocranial surface (Fig. 2C and Fig. 3C), as well as from the endocranial surface (Fig. 2D and Fig. 3D). As noted earlier, the direction of beveling could not be linked in 15 cases because the direction of shooting was not known. Another important issue is then the direction of the beveling. DiMaio [5] stated that when a bullet perforates bone, it bevels out in the direction in which it is traveling. Spitz [7] claimed that symmetrical beveling usually indicates that the bullet struck the skull at a right angle; and asymmetry of the beveling may aid in assessing the angle of fire. To

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explain beveling, some investigators use glass as a model [8,30]. In glass, beveling occurs on the side opposite the direction of the bullet origin, and if the bullet strikes the pane at an angle from the left, the beveling is predominantly on the right [8] However, the present study does not fully support these findings. Table 6 shows that, of the 39 entries, exact correlation between the direction of beveling and of the shooting was observed in only five cases. In the vault, only the occipital wounds displayed this relationship (C17, C18). In the majority of cases, correlation was either partial or nonexistent. Sometimes, beveling was even in the opposite direction to that of the shooting (Fig. 4C,D). In fact, symmetric or asymmetric beveling does not only depend on the direction of fire, but also on the anatomical structure at the site of impact. This includes the variable thickness of the inner and outer tables, the presence of sutures, emissary veins, and foveolae granulares. Furthermore, the most pronounced beveling may result from an asymmetric deformation of the bullet as well as a flattened ricochet bullet tumbling end over end [31,32]. However, the lack of data concerning ammunition in this study makes this explanation hypothetical, and these hypotheses should be empirically tested. In conclusion this series permitted the authors to analyze beveling in entrance wounds. Internal beveling of entrance wounds was present in the vast majority of cases (36 of 39 cases). The absence of beveling is rare, as is true external beveling. Finally, the direction of most pronounced beveling is not always consistent with the line of fire and should not be relied upon to make this determination.

Acknowledgements We are grateful to Dr Joseph H. Davis for his valuable contributions to this study and Dr Susan R. Loth for critically editing the manuscript. The senior author is very grateful to Professor A. Ollier for granting him sabbatical leave and Dean P. Rampal, Faculty of Medicine of Nice, for his encouragement to conduct this research.

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