INCISED WOUNDS

skull fractures, the magnitude of the force needed to cause a blunt tearing of skin leads to blurring of the impact shape, often with radiating or totally irregular tearing. Sometimes the shape is recognizable and probably the best example is a

hammer blow to the head. A circular face may punch out a circle or an arc of a circle, which may also be reproduced in an underlying depressed skull fracture. The exact size of the hammer face may not be accurately reproduced in the lacer- ation, which may be slightly larger than the hammer.

Kicks may cause lacerations, especially if a heavy boot with a hard toecap is used. These tend to be tangential and may peel up a flange of tissue. They can be clean-cut and are sometimes mistaken for knife wounds. Stamping injuries are more likely to cause abrasions and bruises than lacerations, unless the violence is extreme. A heavy focal blow may cause a linear or a stellate laceration, the latter radiating out from the focus of impact. The surface may be abraded and the sur- rounding tissue deeply bruised, so the final lesion is complex.

Firearm wounds are a special form of laceration and will be dealt with separately.

The term ‘incised wound’ usually covers all types of injury from, for example, a knife, sword, razor, glass or sharp axe – though some writers would make stab wounds a separate category, reserving incised wounds for injuries that are longer than they are deep. These semantic variations are not important in themselves, but can lead to confusion in medical and autopsy reports, as well as in oral testimony if the doctor fails to clarify his meaning. The essential feature of all incised wounds is the clean division of the skin and underlying tissues so that the margins are almost free from any damage. Microscopically there is always a narrow zone of injury, but this is minimal compared with the tissue destruction caused by blunt injury. Healing is affected, as well as the extent of subsequent scarring.

Cuts or slashes

When an incised wound is longer than it is deep, it may be referred to as a ‘cut’ or ‘slash’, though a ‘cut’ may also be used by lay persons to describe a laceration. Such slashes when inflicted by knife, sword, razor, cleaver, parang, machete, panga, broken glass or bottle, are typical of a fight, when the assailant strikes out with a swiping action, rather than the thrust of a stabbing attack. They are common in gang fights and bar-room brawls and the weapon may be

swung at arm’s length in a horizontal arc so that if it contacts a body it will slice the skin and tissues as it passes by. They are also seen in suicidal injuries, usually on the wrist or throat. The characteristics of any given wound are a matter of a chance and relative positions. The slash may be deeper at the entry end or the exit point, though it seems true that many such injuries tend to dig in near the point of first con- tact and become progressively more shallow as the wound approaches the distal end. There may be a superficial ‘tail’, a shallow scratch, running out of the termination of the slash, as the weapon rises out of the wound and is drawn across the skin surface before leaving the body altogether.

There is a tendency among advocates to visualize a fight as a static confrontation and to attempt to reconstruct events as if the two participants were standing still, the assailant merely moving his arm. This is an unrealistic interpretation, as all fights are dynamic, with constant relative movement of the bodies and limbs of both parties.

Therefore any relative angles and depths of contact between the victim and the weapon can occur and overinterpretation and simplification should be avoided.

Slashed wounds are less dangerous than stabs, as the rela- tive shallowness of the wounds is less likely to affect vital organs – especially as the arms and face are the common targets. The rib cage and skull protects the chest organs and FIGURE4.32 Transection of a body into two halves at waist level. The victim jumped from a high-rise building and landed on a fence.

brain and the more vulnerable abdomen is seldom the target for a swung knife. Wounds of the neck are the most dangerous and are discussed below. Bleeding is the most serious complication of any slashed wound, though it will be external and more amenable to immediate treatment than the hidden internal bleeding of a stab wound.

A particular form of slashed wound arises from ‘glassing’, that is, the use of a broken drinking glass or bottle as a weapon.

The glass may sometimes be broken prior to the attack, to produce edges that are exquisitely sharp. There may also be spikes of glass, which can inflict deep, almost stab wounds.

Where, more commonly, a glass or bottle is used as a blunt instrument, it may shatter on impact with a victim’s head, and the resulting injuries may both be blunt and incised.

Stab wounds and penetrating injuries

These are of major importance in forensic pathology, as they are extremely common in homicide. In Britain, stab- bing with a knife is easily the most frequent mode of mur- der and manslaughter, primarily in domestic disputes and street violence. A stab wound is an incised wound that is deeper than it is wide. Though many penetrate only the skin and subcuta- neous tissues, those seen by forensic pathologists are most often fatal, having entered vital deep structures. Several aspects of this important topic need discussion.

THE NATURE OF STABBING WEAPONS

Knives are the weapons most frequently involved and their physical characteristics are important in shaping the wound.

A pathologist called upon to examine a knife that may have been used in an assault should note and measure:

■ the length, width and thickness of the blade

■ whether it is single or double-edged

■ the degree of taper from tip to hilt

■ the nature of the back edge in a single-edged knife (for example, serrated or squared-off )

Incised wounds

FIGURE4.33 Homicidal slashed wounds caused by knife; the length is greater than the depth, unlike stab wounds. The long tails are due to the knife rising from the skin, thus indicating the direction of the slash.

FIGURE4.34 A knife slash of the back showing regular scratches along the margin. This was inflicted with a ‘Rambo’ knife, which has deep serrations along the back edge that have somehow marked the skin on withdrawal.

■ the face of the hilt guard adjacent to the blade

■ any grooving, serration or forking of the blade

■ most importantly, the sharpness of the edge and especially of the extreme tip of the blade.

Other knife-like weapons include scissors, chisels, swords, open razors and sharp tools of many kinds, including deliberately modified tools such as sharpened screwdrivers.

Larger cutting instruments such as axes, choppers, parangs, machetes and pangas and agricultural implements such as shears, bill-hooks, hay-knives and many others have been used as stabbing weapons when used by the point rather the long edge.

Spiked instruments come in many forms, from icepicks to hay-forks, from case-openers to fire-irons. The appear- ances of their wounds vary with the physical nature of the implement. Some weapons are exquisitely sharp and the wounds made by them exhibit extremely fine division of the tissues. To razors and razorblades may be added surgical and craft knives, often with a disposable blade, together with carpet and general utility and hobby tools, such as the

‘Stanley’ knife. Equally sharp is broken glass and sometimes porcelain. Both sheet glass and smashed glass utensils can provide edges that equal or exceed surgical scalpels in their cutting ability.

A common weapon in a bar-room fight is a smashed beer tankard, which when held by the intact handle provides a formidable weapon for both slashing and stabbing. Smashed china, such as cups and mugs, can also provide sharp cut- ting edges. The external glaze can project, if the fracture line is oblique, producing a glass-like edge. From personal experiment, the author (BK) has shown that broken china can easily slice through the full thickness of skin and thus validate a defence that injuries were the result of falling on a broken mug.

THE CHARACTERISTICS OF A STAB WOUND

The surface and internal appearances of a stab wound allow the pathologist to offer an opinion upon:

■ the dimensions of the weapon

■ the type of weapon

■ the taper of the blade

FIGURE4.36 Two knife wounds in the back. The wounds have a sharper lower edge compared to a rounder upper edge, due to a one-edged blade.

FIGURE4.35 A stab wound and the inflicting knife. The wound is slightly shorter than the width of the blade at the depth of penetration because of sideways gaping and the contractile elasticity of the skin.

Incised wounds

■ movement of the knife in the wound

■ the depth of the thrust

■ the direction of the thrust

■ the amount of force used.

Dimensions of the weapon

The dimensions of the knife may be a vital part of the investigation of a homicide when the weapon has been removed from the scene by the assailant. The pathologist can sometimes assist the investigators by telling them, within limits, what size and type of knife to seek. When suspect weapons are recovered, his inspection of them may indicate whether or not they are consistent with having caused the wounds in question. As always in forensic medi- cine, however, caution must be employed and the cardinal sin of overinterpretation avoided.

The length of the wound should be measured to the nearest millimetre as it lies undisturbed on the skin. In most instances the wound will have gaped across the centre, to form a long ellipse. The extent of gaping will depend on the anatomical situation, for example, over joints or in the axilla or groin, and whether the axis of the stab is in line with or across the tension of Langer’s lines or underlying muscle bundles.

When the edges are gently opposed, the length of the wound may then extend slightly and should be measured again in this position, which more accurately approximates to the length when the blade was in situ.

An important additional factor, however, must always be taken into account because, when the knife is withdrawn the elasticity of the skin causes it to retract, making the wound smaller than when the blade was in situ. This mechanism may be amplified by contraction of the underlying muscles, which, if at right angles to the axis of the wound, may cause the wound to shorten from end to end, while gaping more widely at the centre. Using wound measurements to predict the size of the knife blade, one must take into account the other matters discussed below, such as movement of the blade in the wound, the taper of the blade and the depth of penetration.

Type of weapon

The type of blade usually refers to whether it had a single or double cutting edge. Most knifes have a single sharp edge, the back edge being blunt or otherwise machined. A few dagger-like weapons have both edges ground to sharpness,

x x y

FIGURE4.37 A stab wound gapes across its width and shortens in length, especially when across skin or muscle planes.

FIGURE4.38 Multiple stabs on the back from the same knife, showing differing shapes and sizes.

some have only the distal part of the back of the blade sharp- ened. On inspecting the skin wound, the pathologist fre- quently finds that both ends of the defect appear sharply cut, coming to a fine ‘V-point’ at the extremities. Unfortunately, this does not necessarily indicate that a knife with two sharp edges was used, as the skin often splits behind the blunt edge to produce a symmetrical appearance.

If, however, there is an obvious difference between one sharply pointed end and a rounded or even square-cut opposite extremity, then it can be said with some confidence that a single-edged knife was employed.

A knife with a thick blade that is squared off to a flat surface on the edge opposite the cutting edge, may some- times be identified from the wound, where a definite double right-angled end to the skin defect is apparent. The skin may split back slightly from each of these corners, forming the so-called ‘fish-tail’ appearance.

Where a knife with a serrated back edge has been used, such as is found on some boy scout or other Bowie-type knives (or the recently fashionable ‘Rambo’ weapons), the back edge of the wound may be torn or ragged and – on some occasions where the knife has entered very obliquely – serrated abrasions may be seen on the skin adjacent to the end of the wound.

If the knife has been plunged into the full extent of the blade, then there may be a hilt bruise or abrasion on the skin surrounding the wound. This may even reproduce the pattern of the guard at the base of the hilt, if there is one.

Careful photography, sketches and measurements are needed to capture the exact outline of such a mark, which are, admit- tedly, unusual.

Taper of the blade

The taper of the blade is naturally related to wound size.

If a tapered blade is inserted to 4 cm, then the length of the wound (ignoring skin retraction for the moment) will be that of the width of the blade at that level. If the taper continues to the 8 cm level, then the wound will be correspondingly longer. Only when the blade edges become parallel will the wound size remain constant for further pen- etration of the knife.

Movement of the knife in the wound

Movement of the knife in the wound can result in loss of evidence as to the size of the blade, but can also add other information. Where a knife is stabbed directly into the body and withdrawn along the same track then, within the limits discussed above, the size of the wound will indicate the minimum width of the blade at the maximum depth of penetration.

If, however, the knife is ‘rocked’ in the wound, the skin defect will be enlarged, sometimes considerably. The term

‘rocking’ means a leverage or angulation in the plane of the wound, so that the cutting edge extends the incision. This rocking can occur either by the knife being actively moved in the wound by the assailant – or by the body moving rela- tive to the knife – or by a combination of the two.

It is sometimes a misapprehension among both doctors and (especially) lawyers, that stabbings and other assaults occur in static circumstances, with the victim standing in the anatomical position. Directions of wounds are all too often interpreted as if the only movement came from the hand of the assailant, whereas in most fatal assaults the FIGURE4.39 A stab wound showing a unilateral ‘fish-tail’ split

caused by the blunt back edge of the knife blade. This is sometimes bilateral due to tearing of the tissues. The other end of the wound is pointed due to the cutting edge of the blade.

FIGURE4.40 Multiple stab wounds from the same knife, showing variations in the size and shape of the injuries. With multiple injuries, it is advisable to number each to facilitate easy reference in the autopsy report and when giving evidence in court.

victim bends, turns and twists, and the assailant often follows with similar gyrations. Thus a knife that is thrust into the body may itself move or the body may move against it before it is withdrawn.

This relative movement may extend the wound in a linear fashion, as described above or there may be twisting of the blade in the wound. In the latter case, the resulting skin incision may be V-shaped or totally irregular. Rarely, a single stab may produce multiple skin wounds, such as a tangential stab of the arm, which passes through the superficial tissues and then re-enters the chest wall. Another instance is a stab through a female breast where, especially if the breast is sag- ging, the knife can pass right through the edge before re- entering the thorax.

Depth of the thrust

The depth of a stab wound may be important in attempt- ing to assess the length of a missing weapon. Again there are pitfalls to be avoided. First, if a knife is driven in up to the hilt, the depth of the wound as measured at autopsy may be greater than the true length of the blade. This is common in the abdomen and to a lesser extent in the chest, because the impact of a forceful stab may momentarily indent the abdominal or chest wall so that the tip of the knife pene- trates tissues that apparently should have been out of reach.

This is particularly so when the hilt guard of the weapon impinges on the skin. For example, the author (BK) has seen the tip of a broken knife embedded in a thoracic spine, where the distance from that tip to the anterior skin wound was less than the length of the blade when recovered.

As with direction, discussed below, the pathologist must also allow for differences in the position of internal organs as measured at autopsy in a supine body, compared with their position in the living body, often in the upright posture.

Such variations in the in vivodistance from the skin wound to the organs penetrated must be taken into account when assessing the depth of a wound. In the chest and abdomen, visceral relationships vary with the stage of respiration. The lower ribs move upwards and laterally, and increase the distance between the skin and deeper structures.

Direction of the thrust

The direction of a stab wound is often a matter of con- tention in homicides, especially as trial lawyers (and their medical advisers) sometimes tend to overinterpret the facts when trying to reconstruct the scene of the fatal assault.

As mentioned above, a stabbing incident is often moving and dynamic, and the victim is rarely in a static, anatomical position. For example, a wound that enters the upper part of the left side of the chest and travels steeply downwards, is not inevitably the result of the killer being taller or situ- ated above the victim, using a downward blow. The victim could equally well have been bending or crouching, the knife then entering on a horizontal plane relative to the floor. All that the pathologist can do is to determine the direction of the wound relative to the axis of the body – it is then a

Incised wounds

FIGURE4.41 A slashed facial wound from a knife, showing undercutting or ‘shelving’ on the edge nearest the mouth, indicating the angle of the knife relative to the surface. The tailed nature of the lower end also indicates that that knife was drawn downwards across the face.

x y x

y

FIGURE4.42 Forcible stabbing can indent the body surface so that deep structures can be injured that appear to be beyond the reach of the knife.