A bite mark on the skin is a patterned injury, reflecting the unique characteristics of the teeth that created it. This injury results from pressure and sometimes suction, leaving specific visual evidence. Analyzing a bite mark involves measuring its dimensions and identifying the types of tissue damage present. The initial appearance and how it changes over time provide information about the source of the mark and when the injury occurred.
Distinguishing Adult and Child Bite Marks
The size and shape of a bite mark are primary factors in differentiating between an injury inflicted by an adult and one made by a child. The major measurement used is the inter-canine distance—the space between the marks left by the canine teeth. A child’s bite mark, typically from deciduous (baby) teeth, generally presents with an inter-canine distance of less than 25 millimeters. In contrast, an adult bite mark often shows a significantly wider distance, typically ranging from 30 to 45 millimeters. The child’s dental arch is smaller and more rounded compared to the adult’s larger, often U-shaped arch, and these features help determine the likely age range of the individual who caused the injury.
Visual Characteristics and Injury Patterns
A bite mark is a collection of distinct lesions that combine to form a recognizable pattern. The most common feature is a contusion, or bruising, which appears as two opposing arches of discolored skin where blood vessels were ruptured by the force of the teeth. These arches are often oval or circular, with a typical diameter between 25 and 40 millimeters.
Within the pattern, individual tooth impressions may be visible, particularly from the six front teeth of the upper and lower jaw. Incisor teeth tend to leave rectangular marks, while the canines may produce rounder or oval indentations.
A second type of injury often observed is an abrasion, a superficial scraping of the skin caused by the teeth slipping against the tissue. More severe injuries, such as a laceration, are cuts or tears that occur if the biting force is high or if there is a grinding motion.
Another specific pattern is the “suction” or “hickey” effect, recognized by a central area of bruising within the ring of tooth marks. This central ecchymosis results from negative pressure created when the biter’s tongue and lips apply suction. The combination of outward pressure and inward suction creates a doughnut-like pattern with a bruise at the center. The appearance and clarity of these patterns depend heavily on the severity of the bite, the location on the body, and the elasticity of the skin.
Aging and Healing of Bite Marks
The color of a bite mark changes over time, providing a chronological clue for estimating when the injury was inflicted. Immediately after the bite, the contusion appears red or reddish-purple due to oxygenated blood leaking from damaged capillaries. Within the first one to three days, the mark darkens into shades of blue or purple-black as hemoglobin breaks down.
As the healing process continues, the mark transitions through different colors. The bruise may take on a greenish hue, typically appearing between days five and seven. Subsequently, the mark shifts to a yellow color, indicating the bruise is nearing the resolution stage.
Abrasions and lacerations heal following a different course, initially forming scabs over the damaged tissue. These scabs protect the wound and generally fall off within one to two weeks as the underlying skin regenerates. While the bruise fades entirely, deep lacerations may leave a scar or an area of hyperpigmentation.