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King County Sheriff

Leadership, Integrity, Service, Teamwork

   King County Sheriff

Emergency: Call 9-1-1

Call (206) 296-3311 24-hours to report a neighborhood problem or a crime that is not an emergency.


King County Courthouse
516 Third Ave
Room W-150
Seattle, WA 98104
(206) 296-4155
TTY Relay: 7-1-1
sheriff@kingcounty.gov

 

 

 

 

 

 

 

 

 

 

 

The Basics of Fingerprint Science

The two fundamental principles of fingerprint identification are that fingerprints are permanent and unique: fingerprints never change and no two fingerprints are the same.
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Permanence:
Fingerprints are formed before birth, and while they grow larger throughout a person’s life, their basic structure remains constant.  They can be temporarily obscured when the skin is damaged; but once healed, the ridges grow back in the exact same pattern.  Even when a fingerprint is permanently scarred, there is almost always sufficient detail around the scar to allow for a positive identification. 

Uniqueness:
Fingerprints are made up of skin ridges that have three main features: ridge endings, bifurcations, and dots.  Ridge endings are points where the skin ridges stop and a new ridge begins.  Bifurcations are points where a single ridge splits into two ridges forming a Y-shaped pattern.  Dots are pieces of a ridge that are so small they look like a dot.  There are often hundreds of these “points” on one finger.  The relationship between each of these points and the surrounding ridge detail is so complex that no two fingerprints have ever been found to be exactly alike. 

Fingerprints vs. DNA
Both fingerprint identification and DNA analysis have proved to be valuable tools for personal and criminal identification.  However, fingerprint identification can be more accurate than DNA analysis.  Even identical twins that look exactly alike and have the same DNA structure will always have different fingerprints!  This is because fingerprints are formed in the womb, where movements and natural growth randomly create the characteristics.