There is also considerable room for research on the various factors that affect the quality of latent prints (e.g., condition of the skin, residue, mechanics of touch). Formal research could provide examiners with additional tools to support or refute distortion explanations. Currently, distortion and quality issues are typically based on “common sense” explanations or on information that is passed down through oral tradition from examiner to examiner. A criticism of the latent print community is that the examiners can too easily explain a “difference” as an “acceptable distortion” in order to make an identification.³⁸

Other pattern evidence, also referred to as impression evidence, occurs when an object such as a shoe or a tire leaves an impression at the crime scene or on another object or a person. Impressions can be either two dimensional, such as shoeprints in dust, or three dimensional, such as tire track impressions in mud. Shoeprints and tire tracks are common types of impression evidence examined by forensic examiners, but the list of potential types of impression evidence is long. Examples include bite marks, markings on bullets and cartridge cases, ear prints, lip prints, toolmarks, some bloodstain patterns, and glove prints.³⁹ Although there are general approaches concerning the analytical sequence of various types of impression evidence, each has its own set of characteristics. For example, some types of impression evidence, such as those arising from footwear and tires, require knowledge of manufacturing and wear, while other types, such as ear prints and bloodstain patterns, do not. Because footwear and tire track impressions comprise the bulk of the examinations conducted, the remarks in this section are specifically focused on these analyses. Bite marks, markings on bullets and cartridge cases, and bloodstain patterns are covered in later sections in this chapter.