FORENSICS 112: OUCHES, LARGE AND SMALL (Part 1)
Assaults of all kinds can result in body wounds, and most involve skin damage. Our skin just seems to hang around not doing much, but it performs some very important functions. It stands between us and many harmful agents. It also plays important roles in maintaining our body temperature and in gathering sensory information from our surroundings.Skin comprises an outermost layer known as an epidermis. Its thickness ranges from 0.05 mm eyelids to 1.5 mm palms and soles, and pigment (melanin) is produced within it. Cells of the innermost of its five sublayers divide and push previously formed cells upward, where they gradually flatten, die and slough off.
Below the epidermis is a dermis layer. It provides a home for capillaries and nerves, the nerves transmitting touch, pressure, pain, itch and temperature sensations. Also within the dermis are sweat glands and hair follicles. Oil (sebaceous) glands and odor glands also reside there and are associated with the hair follicles. Below the dermis is a subcutaneous (hypodermis) layer, which connects the skin to whatever is below it. It contains a layer of fat (at least some in every one of us) and blood vessels that supply and drain the capillaries in the dermis.
An examination of body wounds can provide valuable information relating to the manner of a person’s death and to the contribution each made toward that death. Photographs of wounds and a nearby, readable measuring device provide means for later estimating wound dimensions. Of obvious additional importance is a report accurately describing the wounds and their locations with respect, for example, to how far left or right they are of the body’s midline, how far below certain vertebrae and how far above the ground they are. The distance above ground can, of course, be one factor in identifying a make and model of vehicle that struck a victim.
Wounds can generally be forensically defined as tissue damage resulting from being shot, stabbed, struck, strangled, or bitten by someone, from being struck by a vehicle, from having fallen, or from having lit a dynamite fuse that was a tad too short. Wounds can also be generally categorized as being abrasions, bruises, contusions, incised wounds or lacerations; and it is common for a body to display more than one type of wound. This essay addresses the first two types.
An abrasion is what most persons would refer to as a “scratch.” It is a superficial injury; and, since its damage is generally limited to the top skin layer (epidermis), it rarely bleeds much, if at all. Active children often display abrasions on their knees and elbows. Wounding forces that cause abrasions act primarily along the surface of skin rather than toward it. If substantial force is directed toward the skin, the resulting wound is referred to as a “crush” injury. Toppled motorcycle riders often suffer abrasions on various parts of their hides while using those parts as brake pads as they skid to a stop. Many of us have experienced what is known as a rope or friction burn when a rope slides quickly through our hands. A hurrying dental technician whipping a piece of dental floss from between one’s teeth can burn one’s gum in a similar manner. (Are you dental technicians out there paying attention to this?)
Just as snow is piled at one end of a run by a snow plow, dislodged epidermis is piled at the terminal end of an abrasion. This indicates the direction of the causing force. Jagged edges of the abrasion can also point in the direction of force. Of even greater consequence, abrasions sometimes preserve, for example, images of items that created them; and photographs of the images can be compared later to vehicle bumpers, grilles, hood ornaments and the like.
A closed wound known as a bruise, or contusion, refers to an area of hemorrhage that suffered a leakage of blood from blood vessels at the capillary level into surrounding tissues. Types of bruises include petechial hemorrhages, which involve pinpoint marks where blood extravasates (escapes) from vessels. Such can be caused by blunt trauma, pressure to the neck or chest, or simply by violent coughing, sneezing or even suction (as with a hickey).
An extravasation of blood within the dermis but below the capillaries, causing the blood to extend into subcutaneous tissues, results in a bruise having indistinctly appearing edges. Extravasation occurring closer to the surface of the skin results in what is known as an intradermal bruise. A bruise caused by an object having grooves or ridges, such as a ring or a woolen glove covering a fist, can produce a sharply defined, red profile of the object. This type of wound is referred to as a “patterned” injury, and a photograph of the bruise can be compared later to suspected objects.
Bruises caused by cylindrical objects such as pipes and bats produce a pair of parallel, linear bruises caused by the stretching and tearing of blood vessels along edges of the impact area. The bruises are separated by a pale, central area. Such bruises are referred to as tramline bruises. Bruises caused by spherical objects produce circular bruises for the same reason. A group of small round or oval bruises on an arm, a leg, a face or a neck could be the result of someone having been manually restrained, silenced or choked. Defensive bruises on forearms and upper arms indicate attempts to fend off an assailant’s blows.
Bruises are not limited to surface tissues. Bruises can be created within tissues and organs below the skin surface. Periosteal bruises are bone bruises, and they can be severe and quite painful. It is important in forensic autopsies to search for all possible indications of trauma, and that includes bruises beneath the surface of the skin. This might require removing all skin covering a suspected area and special dissection procedures.
The age of bruises, especially if child abuse is involved, can be important. Varying physical factors prevent accurately pinpointing a time of injury; but, due to the degradation of hemoglobin in blood, bruises gradually change color. The sequence of bruise colors reported vary from one report to another but generally runs from red or violet to blue to green to yellow. There is some agreement that a bruise that is green or yellow is at least 18 hours old. A person having bruises of significantly different colors, which suggests that they were inflicted at different times, may well have been a victim of prolonged abuse.
Extra facts
Persons taking blood thinners such as aspirin tend to bruise more readily.
Blood accumulating under the influence of gravity can appear some distance from an actual site of a trauma. Such an appearance behind and below the ear or around the eyes can result from a basilar skull fracture. Bruising around the eyes are known as “racoon eyes” or “panda eyes.”
Robert C. Jones
