Overview of Impression and Pattern Evidence

NIST has launched an NIJ-funded open-access research database of bullet and cartridge case toolmark data.

Impression Pattern and Trace Evidence Symposium

View on-demand presentations from past NIJ-sponsored symposia.

One of the most common forms of evidence investigators may detect and collect at a crime scene is impression and pattern evidence.

Impression evidence is created when two objects come in contact with enough force to cause an "impression." Typically impression evidence is either two-dimensional — such as a fingerprint — or three-dimensional — such as the marks on a bullet caused by the barrel of a firearm.

Pattern evidence may be additional identifiable information found within an impression. For example, an examiner will compare shoeprint evidence with several shoe-sole patterns to identify a particular brand, model or size. If a shoe is recovered from a suspect that matches this initial pattern, the forensic examiner can look for unique characteristics that are common between the shoe and the shoeprint, such as tread wear, cuts or nicks.

Impression and pattern evidence can help link a suspect or tool to a particular crime scene. New or improved techniques to identify, collect, analyze and preserve impression and pattern evidence would greatly aid the forensic community. NIJ funds the following impression and pattern evidence research:

• Studying the effects of time and environmental factors, such as weather damage, on forms of impression evidence.
• Investigating unique characteristics that may distinguish one type of impression evidence to the exclusion of all others (e.g., what characteristics make a fingerprint unique).
• Developing sophisticated tools to take precise physical measurements of evidence.
• Improving the National Integrated Ballistics Information Network.

Learn more about fingerprints:

• Overview of Fingerprints
• Fingerprint Database Interoperability
• Effects of Human Factors on the Accuracy of Fingerprint Analysis.

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