Evidence Collection from the Patterned Injury/Bitemark
DNA swabs of the injury should be properly collected as soon as the injury is discovered. Only persons with knowledge and experience in the correct protocols for DNA collection, handling and storage should be utilized for this process.
Photography is the best and most common method of collecting and documenting the appearance of any injury. High quality digital camera systems are recommended; however, technology and capabilities of digital photographic equipment are constantly improving. Thus, no suggestions for a specific type of digital imaging system will be recommended. The photographic techniques involved in the evidence collection should include the following:
Orientation color digital images showing the location of the injury on the body (or the pattern on an inanimate object).
Close up (macro) digital images of the patterned injury with and without a photographic scale. It is recommended that the ABFO #2 scale be used whenever possible. Placement of the scale should be on the same plane and adjacent to the injury so as not to overlap or cover it. The surface of the lens should be as parallel to the injury as possible to avoid parallax distortion.
If the injury is on a curved anatomical location, digital images from different orientations around the injury will be necessary to adequately document the pattern.3
Specialized photographic techniques include alternate light source imaging (ALS), infrared (IR), reflective ultraviolet light (UVA) protocols and indirect lighting techniques for injuries that may contain three dimensional properties. It is beyond the scope of this course to give detailed explanations for these specialized photographic techniques; however, there are many textbooks and other references that describe how to employ these techniques.
Repeated photographic sessions to observe changes occurring in the injury over time (days in the deceased or up to a month in living tissue) may be employed until all attempts to capture the details of the injury have been exhausted.3
Impressions of the Injury:
If a patterned injury contains three dimensional properties, an impression of the injury should be made. The impression material should be a polyvinylsiloxane (PVS) type dental impression material and should be rigid enough to reproduce and maintain the three-dimensional properties of the injury. A rigid backing material, such as dental stone, is frequently used as a stabilizing framework to minimize distortion of the impression material.