Introduction
One of the purposes of the medicolegal system is to protect the innocent and prosecute the guilty. Evidence is needed to try the accused. An analysis of trauma that may have caused death to the victim is an important step in this direction. It may also give information about antemortem injuries such as those resulting from accidents, child abuse, torture or other human rights violation. The term trauma may be defined in a number of ways. However, it is the response of the body against any sudden external insult. It may alter an individual’s life from normal to a functional and esthetic abnormality and may lead to death or irreversible injury to the victim. Determination of the cause of trauma is a difficult task and therefore may be very complex to explain. The problem may be worse if the remains are skeletonized or in a state of advanced decomposition.
Anthropological literature classifies trauma by its origin into dental trauma, fractures, dislocation, scalping, surgery, perimortem cuts and breaks, and weapon wounds. Some of these categories are primarily antemortem in origin (e.g. dental trauma, fractures, dislocations) and may not be responsible for acute death. Some (e.g. surgery) are handled in hospitals. Of the remaining, perimortem cuts and breaks and weapon wounds are of immediate concern for forensic scientists, particularly if the victim died because of them. Once the trauma is classified as such it must be assessed in terms of its relation to death. So, a trauma can be considered antemortem, perimortem or postmortem. Trauma-like appearance of the skeleton may also be caused by other agents such as animal or other environment events.
No matter what the origin of trauma it must be assessed with suspicion within the perspective of legal sciences. The ultimate aim of such an assessment is to determine not only the cause of the damage but also the manner of death. The purpose of this article is to discuss the causes of trauma that are observable from the skeleton and their implication in forensic sciences.
Cause and Manner of Death
In the case of a crime involving injury or death, the cause must be established. If the victim dies from it, the manner must be decided. Terms cause and manner have specific meanings in forensic medicine. The cause may be defined as an injury or disease which may lead to death. Gunshot wound to the head is a cause that will often kill the victim.
Manner is the classificatory system of death and can be one of four main and classical assessments: natural, accidental, suicide and homicide. The decision as to which one of these is to be considered as the manner is made by the authorized individual, e.g. medical examiner or coroner. The coroner (or medical examiner) in turn needs the advice and evidentiary support from the pathologist, anthropologist, criminalist and others, who are involved in the investigation, and have expertise of the crime and scene where the deceased is found, and have expertise to explain what may have killed the victim. Using the gunshot wound as the cause of death as an example, the manner can be one of several. The victim may have killed himself/herself with a single shot into the mouth and thus it may be considered suicide. The person may have been shot from the back of the head several times by an assailant. This suggests homicide. The gun may have been accidentally fired while cleaning. Natural deaths may occur for a number of reasons including malfunctioning of vital organs such as heart attack and other acute diseases, or terminal death resulting from chronic diseases.
In order to make decisions about the manner, a number of issues must be resolved. There are two kinds of remains that may shed light into the cause of death. The first, includes those that have an obvious cause of death, e.g, a bullet hole in the head. This type of case is not considered circumstantial. It is well known that gunshot wound to the head may kill (and very often it does kill) a person, and the wound has particular entrance and exit characteristics. In the second type there is damage or injury to the skeleton, e.g. marks on the ribs or a broken zygomatic bone. In this case the cause of death may be considered circumstantial, because it is not definite that these marks caused the death. The damages may have been made by a knife, an animal scavenging or something else, and the death may have occurred from another cause.
To determine if the cause is obvious or circumstantial, the crime scene must be very carefully investigated and must not be contaminated by factors such as stepping on evidence or the relationship of scattered artifacts and remains with each other. Forensic techniques, and particularly forensic anthropological (archeological) techniques are essential to analyze a crime scene. It is also important to positively identify the victim in order to solve a circumstantial death case. In situations where the scene is the remains of a highly decomposed person, it is of benefit to the coroner to invite a forensic anthropologist who is competent in archeology and osteology. A forensic anthropologist is a consultant to the legal system and commonly involved in suchcrime scene assessment and identification of the deceased. In order to determine whether a particular trauma is death related or antemortem or what the manner of death is, his/her assistance is essential.
In general there is a tendency by crime scene police to underestimate the importance of a crime scene where skeletonized remains are found. And yet it is ironic that the same experts are very meticulous when they deal with the scene where a recent crime has occurred.
Wound Assessment
Antemortem trauma may be obvious when there is healing, inflammatory process, or periosteitic/osteo-myelitic activity at the location of the lesion. It is well known that the inflammatory process starts very soon after an injury, and may be visible within a few hours, at least at the microscopical level. Bone inflammation, suchas periosteitis and osteomyelitis, is a gradual process and therefore chronic, and the presence of bone reaction and remodeling of the injury indicates that a time period of several weeks or months may have passed since death.
Wound assessment also gives clues in child abuse cases. The victims of this often show healed lines of fracture in their bones, particularly in the ribs. Although various stages of healing have been described, there are many factors that may complicate the problem. These include age, sex, the bone itself (rib, skull, or long bone), the nature of the instrument causing the wound, and even the general health of the victim (e.g. rickets).
There are a lot of pitfalls to be avoided. A healed fracture is obviously an antemortem condition and the person lived some time for the wound to heal. A fresh wound that may have occurred a few weeks before death is thus not an immediate cause of death. Perimortem trauma refers to a wound that may have occurred at the time of death, or a short time before or after death. In perimortem trauma, it is often impossible to determine if the fracture or defect occurred exactly at the time of death. The forensic scientist has to find some clues, such as the presence of hematoma or absence of discoloration at the edges of the fractured area, and other classic perimortem patterns (e.g. gunshot wounds, patterned blunt or sharp force injuries, butterfly fractures).
Hematoma shows the discoloration around the edges of a broken area. Its assessment may be difficult if there is a long time interval since death. The elapsed time not only affects the color of the hematoma which will gradually fade, but also changes the color due to surrounding material suchas the decaying leaves or the soil itself. Nevertheless discoloration in relation to bloodstain of a perimortem fracture is usually very localized, whereas the dark staining by the soil or rotting leaves should be visible not only on that bone but others which are in contact with the plants and ground.
There are several instances in which the problem of wound assessment can be simpler to handle. Recognition of the bleeding of the fractured edges such as that in a hyoid bone may be all that is needed to determine the cause and manner of death. Ecchymosis of the skull is another relevant clue. In this case, blood coming from the broken tiny trabeculae may infiltrate the diploe of the skull vault. This may be readily observed by transillumination of the skull, that is, holding the skull in front of a simple light source, and by microscopy.
Postmortem damage can also be very difficult to analyze. Ribs can easily be broken by a crushing injury or broken by a scavenging dog. An injury caused by a blow to the chest may not be easily differentiated from that caused by a dog or large animal stepping on the remains. Postmortem defects or fractures are very frequent. They are caused mainly by environmental factors, including soil chemical and mechanical erosion, exposure to sun and water, plant activity, and animal activity. Rarely the cause of postmortem alteration is a postmortem trauma due to human activity.
A careful crime scene investigation can give some answers to the problem. It provides important clues about the damaged bones and whether remains were scattered when they were discovered. In this way the footsteps of a cow or horse can be differentiated from a blow on the chest by a baseball bat, metal pipe, or some other blunt object.
Wound Classification
Trauma can be classified into gunshot wounds; sharp force injuries; blunt trauma; and burnt bones. In fact the various trauma encountered routinely are a wide range of combination of these four elementary lesions. Of these the first three are made by an instrument or a weapon, and sometimes by the head, hands or feet of the assailant.
Burnt bones are relatively simple to recognize (but their forensic analysis raises a great deal of issues) and are described elsewhere.
Gunshot wounds
Most of the research on trauma has been the assessment of gunshot wounds. A gunshot wound has a number of characteristics. The most obvious ones are the entrance and eventual exit holes. Each hole in a skull has a unique appearance of outer and inner tables (external and internal openings) of an entrance hole.
The exit holes also have internal and external openings. The exit hole is morphologically different from the entrance. The entrance is typical when it is round or ovoid shaped, sharp-edged of punched-out appearance, and interiorly beveled. The exit is highly varied depending upon which bone the bullet exits and whether the bullet is jacketed or not, but is usually larger than the entry wound, and more irregular. Jacketed bullets should make less damage to the skull. If the exit is through one of the thin bones as those of the face, the whole area may collapse and there may be no sign of which of the bones was hit first and could become very difficult to interpret.
It should be noted that exit and entry wounds are better known and thus assessed for the skull than for the postcranial skeleton. This is probably because of the skull’s anatomical shape (a globe with two tables separated by the diploe). Even large bones like the pelvis and scapula do not show the same gunshot wound opening characteristics as those of the cranium.
Tangential shots are those that make a grazing defect on the surface of the bone and then deflect away. This occurs only because the angle of trajectory is very small. These wounds are relatively easy to recognize on the surface of the skull or postcranial skeleton. However, the skull wounds are more complex and varied. Tangential wounds may vary from a simple grazing creating an oval-shaped nick (e.g. on the skull) or a semilunar defect (e.g. on the edges of a rib). Sometimes a part of an irregular bone is broken off. This category can be exemplified with the breakage of the transverse process of a vertebra or the zygomatic process of the temporal bone. The bullet may hit the surface of a bone with a very narrow angle and thus continue grazing until it forms a groove. This may occur more commonly in bones with a flatter surface like the bones of the skull vault or the man-dibular ramus. Although these three types of tangential wounds may be seen in the entire skeleton, the skull shows further variations which usually are considered as guttered and keyhole defects. The skull shows an outer and inner table separated by diploe. Because of this the wound formation varies. In essence a tangential wound may be seen only on the outer table. Sometimes both tables are affected. However, the inner table lesion may be due to the pressure arising from the impact on the outer table. In a third case the inner table exhibits a defect, but the bullet exits the skull without a massive fracture.
Keyhole defects are typical but relatively rare. The bullet hits the skull at a shallow angle and splits into two parts immediately. One portion penetrates the skull and explains the occurrence of a typical entry wound with internal beveling. The second portion is deflected and explains the occurrence of an exit wound with external beveling, connected to the entry wound.
The angle of the shooting can also be deduced from the skeleton, the skull being a better indicator than the postcranial skeleton unless several bones (e.g. sternum, ribs and a vertebra) are fractured along the path of the bullet. In the latter case one can determine the direction with a simple knitting pin. In the cranium, the shape of the entrance hole and beveling are of great importance. A circular entry and symmetrical beveling suggests, for example, a right-angle shot. Oval or oblique entry suggests a narrow angle between the direction of the bullet and the surface of the damaged area of the skull. In other cases, though rare, grazing, gutter wounds or keyhole indicate a tangential shot.
The direction of the shot is deduced from the entrance and exit holes as the path is usually straight between them. This direction is described by giving the angles in reference to a sagittal and horizontal (Frankfort horizontal) plan, and the right/left direction, on an individual standing in the standard anatomical position. Radiographs are important, especially when there is no exit. Autopsy and radiographs can detect the projectile or its fragments within the brain. Metallic ‘snow’ is a classic appearance in the radiographs. Sometimes the pathway is quite amazing. A bullet may follow the curvature of the skull for a long distance, or strike a rib at an angle and encircle the chest, and possibly exiting the opposite side without having penetrating the pleural cavities. Sometimes the bullet penetrates the heart and travels down the femoral artery. These erratic pathways may complicate the interpretation of the death scene, especially from skeletonized remains.
The range of fire is another important issue. Finally the production of fractures is dependent on the range at the time of discharge and the kinetic energy possessed by the bullet, as well as the shape of the missile when it perforates the skull. Fractures are very common in contact wounds in the head, due to the gas expansion. The primary fracture is the hole. The secondary fractures are radial fractures, which try to dissipate the kinetic energy. If this is insufficient, tertiary concentric fractures occur. Multiple shots to the head may be assessed by the arrangement of some fractures that are interrupted by others.
Sharp force injuries
A cut or incised wound is seen when a sharp-edged object (weapon, object, any sharp instrument) is drawn over the skin: the injury is longer than it is deep, and the force required is slight. Exposed portions of the body are often involved: head, neck, arms. In sharp force injuries the sharp tool cuts and divides as it penetrates, whereas in blunt trauma there is a crushing or tearing of the tissues. Incised wounds in bones are usually seen on ribs and vertebra. In ribs they are seen in association with fatal chest stab wounds, and similar injuries of the anterior aspect of cervical bodies can be produced by deep slashes on the upper extremities. In hands they are often interpreted as defense lesions. The length of the lesion is really more than the depth; usually the cutting into bone is very superficial because of its hardness. Incised wounds from edged weapons display a straight and even profile when magnified.
Stab wounds are due to bone percussion, more or less at a right angle, with a sharp or partially sharp pointed object; a pointed instrument penetrates more or less deeply, and the wound is deeper than its length. In bones they can be called punctures. The tip of a sword is a good example, but more common examples include the tip of a knife, scissors, screwdriver, but also glass, nail etc. Most of stab wounds are associated with homicides, and the thorax and abdomen are often targeted. The lesion is roughly linear and deep, resulting in a tiny point depression up to a localized large area of multiple fractures. Sometimes the tip of the blade breaks off and remains embedded in the bone.
Chop wounds are inflicted by heavy and sharp instruments (e.g. axes, machetes, meat cleavers). Most chopping wounds are also seen in murder cases. The chest and abdomen are rarely targeted. In contrast exposed portions of the body are often struck ( e.g. head, face, neck, shoulders, and extremities). Very often the death is immediate and due to shock and hemorrhage. The injury has about the same size as the cross-section of the penetrating implement. There is a combination of cutting (sharp force injury) and crushing or compression (blunt force injury) mechanism, therefore the edges are sharp (incised appearance) and irregular (blunt trauma). In bones one can expect a patterned groove with two walls and a floor, or a depression with multiple communitive fractures. The cranial surface may be depressed and display a wound which is almost an exact reproduction of the cross-section of the blade. In limbs a bone break is possible which may indicate the direction of the blow. However, the fact that the assailant, the weapon, and the victim are all independently in motion may give a twisting mechanism which could complicate the interpretation of the lesion.
The results of chopping insults are partial or complete amputations of fingers or toes, hands or feet, fractures of limbs at various levels, severe lesions of joints up to a complete disarticulation, and sometimes a glancing blow if there is a tangential strike of the weapon. Other sharp force injuries exhibit complex lesions: electric saws, serrated knives, propellers and so forth. Saws involve rare situations of postmortem dismemberment and mutilation. Multiple repetitive movements produce peculiar tool marks.
Blunt force injuries
Blunt trauma are usually caused by a direct blow (with a blunt weapon of which the most frequent is a natural object as the fist or a blunt tool), a fall on the ground or on an object, and a compression, as when a part of the body is passed over by a vehicular wheel. The lesion is produced by an impact of the body on a smoothor flat surface, or an impact on the body by a smooth(as a bludgeon) or flat instrument. Therefore a blunt impact tears, shears and crushes. The severity of the lesion depends on several factors, mainly the force delivered by unit of surface and time, and the nature of the surface or weapon.
The mechanisms which cause blunt trauma include compression, tension, bending; and twisting. Most often all four mechanisms may work together to create the trauma. In compression of a long bone, the force is applied onto the axis. The bone tends to fail in oblique angles. This axial compression gives a 45° angle with the line of fracture. Compression is also very frequent in cancellous bone such as the vertebral body. Tension is the opposite mechanism. The bone is stretched in the direction of the axis, and the bone usually exhibits a transverse line of fracture. Pure forces of tension are rarely seen, except when a tendon or ligament exhibits a strong and fast force (e.g. the malleolus of the ankle). In bending there is tension on the convex side, and compression on the concave side of the bone. A butterfly fracture is not rare in these circumstances. In twisting the force is exerted in a spiral direction, and results in very complex shear-stresses, tension and compression stresses, applied to the bone.
In forensic pathology one distinguishes between direct trauma and indirect trauma. Direct trauma (e.g. by a blow with a stick) has specific characteristics: skin lesions in front of the fracture; transverse fractures, usually at the same level on the two bones of arms or legs. In contrast indirect trauma shows no skin lesion: e.g. in oblique or spiral fractures, if the two bones are fractured, the fractures are not at the same level; usually in these cases the mechanism is proved to be indirect, such as a fall or torsion of a limb.
The recognition of blunt lesion is often possible by a careful analysis. Ragged edges and crushing along the margin of a defect indicate a blunt force injury rather than a sharp force. Sometimes the edges of the bone have to be examined under magnification. On the skull, flakes of outer table are due to the levering action of the implement while it is inserted in the wound, and is seen with a chopping instrument, or very heavy blunt strike which may push the bone plates inwards. Delamination of the outer table is a sign of blunt trauma.
In blunt trauma of the head, the plates of bone produced by the radiating fractures are forced inward, and the eventual concentric fractures are beveled internally (in contrast, in gunshot wounds, the plates of bones are levered externally by the intracranial pressure). The results depend on the rate of loading. A slow rate may give a plastic permanent deformation of the plates of bones. The fractures can be redirected, following the weakest pathways. An interesting feature in skull is the occurrence of a bone patterned lesion (indenting fracture), whereas bursting fractures display radiating and concentric fractures. Ring fractures of the base of the skull are peculiar, usually due to the compression of the skull vertically against the spine. Face trauma is very frequent, especially during traffic accidents. Each bone of the face may be affected. Other bones such as the hip and vertebra have their own mechanism and fracture pattern. In general though, a blunt trauma leaves bruises (even in bones), fractures, and dislocations.
Location of the Trauma
Skull trauma is very particular because of its anatomy (the skull is a closed box, and has two tables separated by the diploe). Some parts of the face act as a fender and other parts as a buttress and are thus able to redirect fractures. This may explain why skull lesions are different from those in other bones. Some of these include: dissipation of the energy by radial and concentric fractures; redirection of fractures by buttressing; the possibility of plastic deformation in slow loading cases; trends to lever the plates of bones inwards in blunt trauma, and outwards in gunshot wounds; the possibility of shattering of the skull into multiple pieces, because of the increase of intracranial pressure; the occurrence of internal beveling of the entry wound, and external beveling of the exit wound (in gunshot trauma); difficulty to interpret some lesions occurring on thin parts of the skull (like the thin plates of the orbits); occurrence of contrecoup fractures, occurring at a location away from the point of impact, due to an undulation of the skull vault.
Postcranial trauma differ from those of the cranium. For example a bullet easily passes through the postcranial body especially the abdomen and chest and yet may leave only a few nicks and cuts and sometimes nothing in the bone. Bullets may create tunnel-like damage in larger vertebrae (lower thoracic and lumbar), but very often a piece of the bone is broken off (e.g. vertebra). A bullet usually breaks a rib into two pieces. Beveling is not a rule but is possible in thick bones like the femur and humerus, and even in vertebrae, ribs, and rims of the orbits or of the zygoma processes. These cases are of great interest because they indicate the direction of the trauma as in the skull. Sharp force injuries may also leave clues on various bones. Cutting or stabbing lesions are important evidence. They may be also analyzed in terms of direction (i.e., from front to back or left to right), when several bones are struck (e.g. an anterior surface of a rib and a vertebra). In these cases one has to reconstruct the pathway and assess which organs or arteries were struck. This can lead to the conclusion that a knife injury probably caused death. Some locations indicate defense wounds (fingers of the hands, or cutting marks on the forearms).
Discussion
Assessment of bone trauma is a very important aspect of forensic pathology and anthropology. On skeletonized remains, soft tissue analysis is not possible, but lesions can persist in bones. Therefore an analysis of bone trauma may lead to an understanding of the cause and manner of death, and to some extent assist the investigator to reconstruct the death scene.
From a practical point of view, the lesions encountered are made by a combination of factors suchas gunshots, sharp forces, blunt objects, and sometimes heat such as fire can also insult the bone. Any bone lesion must also be assessed as antemortem, perimortem, or postmortem trauma. Sometimes, this can be very difficult because some lesions can occur both during and after death.
Gunshot wounds are usually recognized by specific features belonging to the entry wound, i.e. round or oval in shape, outer clean and punched-out appearance and, internal beveling. These specific features are frequently seen in skulls, at least in the neural part of the skull where bones are thicker. Exit wounds in a skull are not always seen (if the bullet remains within the brain), if present they are usually larger than entry wounds, and nearly always irregular. Wounds exhibit a wide range of shapes, sizes, and other unusual features. These shapes may be due to the nature of the bone itself (its thickness, softness, disease), the bullet (velocity, range, intrinsic features of the bullet, cross-section as it strikes the bone), the interaction between both (e.g. the angle between the bullet and the bone), and other factors.
Sharp force injuries are divided into cutting, stabbing and chopping lesions. Cutting lesions of bone are very superficial and longer than deep due to a sharp blade. Stabbing in bone leads to a well delimited puncture, with a patterned lesion, displaying the cross-section pattern of the blade which has struck the bone. Chopping wounds, due to heavy implements like an axe, act by a double mechanism (sharp force and blunt force injury). Unusual features are frequent, because of blade types, such as serrated knife, double-edged knife, or more commonly of the various sharp or pointed objects, which are involved in bone lesion. Another difficulty of this analysis is represented by the constant moving of the assailant and/or the victim during the assault.
Blunt force injuries are the most frequent lesions encountered in forensic sciences. By definition the instrument does not exhibit a sharp edge, and the mechanism is only an impression of bone. Cortex is compressed below the injury in blunt trauma: in sharp force injury, the compression is weak and cortex is compressed to the side. The compression increases in chopping wounds, because the two mechanisms, sharp and blunt, are involved. Blunt force results in ragged edges of the lesion. Blunt trauma gives the notions of elastic (reversible) and plastic (permanent) deformation, with the tension and compression sides of the trauma. Tubular long bones behave in a manner resembling tubular beams. Therefore, the recognition of the tension and compression sides helps to assess the direction of the trauma, which is from compression side to tension side. Skull fractures are complex, because the inward displacement of the bone (due to the impact) may induce some outward displacement, and may explain the occurrence of fractures at a distance from the point of impact (at which there is sometimes no damage at all). In the skull, areas of buttressing redirect fractures, whereas cranial sutures and vascular grooves are areas of lesser resistance. The patterned feature of some blunt trauma may help to assess the general characteristics of the weapon, or more precisely the cross-section surface of the weapon. The internal beveling of the concentric fractures in skull are explained by inward forcing of the plates of bones (produced by the radiating fractures). This can help to recognize the direction of the force: for example if the head is shored on one side and struck on the other, internal beveling is seen on both sides, because the direction of force is bilateral. Slow loading involves the bone to fracture in plastic deformation, and the bones remain permanently deformed; this situation is seen when the head is run over by a car tire. As for fractures in gunshot wounds, the rule of crossing determines the sequence of multiple trauma to the skeleton, as the second fracture is interrupted by the first one.
