Patterned Evidence

Patterned evidence is one of the most commonly recovered forms of evidence, according to the National Institute of Justice (NIJ).[1] Impression evidence, which is a type of patterned evidence, forms when objects come into contact with one another, leaving either a two- or three-dimensional mark. A fingerprint on a hard surface is an example of a two-dimensional mark, while a tire impression in mud is an example of a three-dimensional impression. Patterned evidence is analyzed and matched in order to link a suspect or tool to a crime. Unique characteristics, such as cuts or nicks, within a piece of patterned evidence allows for stronger matching, such as when a crowbar is used on a windowsill. The matching of patterned evidence from an unknown sample from the crime scene and known sample from the suspect is done by a trained examiner, who must identify unique characteristics and determine whether the samples may have come from the same source. Handwriting, fingerprints, tool marks, ballistics, bloodstains, and other impressions such as shoe prints or tire marks are examples of patterned evidence. Fingerprint evidence is a common form of patterned evidence; potential matches can be found using a fingerprint database like the FBI’s Integrated Automated Fingerprint Identification System (IAFIS).

Refer to chapter 5 of the 2009 NAS report on forensic science for further descriptions of disciplines: friction ridge analysis, tool mark and firearms identification, bloodstain pattern analysis, and other pattern/impression evidence: shoeprints and tire tracks.[2] Refer to chapter 10 of the 2009 NAS report on forensic science for more information about automated fingerprint identification systems.[3]