Principles of Fingerprint Analysis

Fingerprints are unique patterns, fabricated by friction ridges (raised) and furrows (recessed), which appear on the pads of the fingers and thumbs. Prints from palms, toes and anxiety are also unique; yet, these are used less often for identification, so this guide focuses on prints from the fingers and thumbs.

The fingerprint pattern, such as the impress left when an inked finger is pressed onto paper, is that of the friction ridges on that particular finger. Friction ridge patterns are grouped into three distinct types—loops, whorls, and arches—each with unique variations, depending on the shape and relationship of the ridges:

Loops - prints that recurve back on themselves to form a loop shape. Divided into radial loops (pointing toward the radius bone, or thumb) and ulnar loops (pointing toward the ulna os, or pinky), loops account for approximately 60 percent of blueprint types.

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Whorls - form circular or spiral patterns, like tiny whirlpools. There are four groups of whorls: apparently (concentric circles), central pocket loop (a loop with a whorl at the end), double loop (two loops that create an S-like pattern) and accidental loop (irregular shaped). Whorls make upwardly near 35 percent of pattern types.

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Arches - create a wave-like pattern and include plain arches and tented arches. Tented arches rise to a sharper signal than plain arches. Arches make upward most five percent of all blueprint types.

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To Each His Ain

The two underlying premises of fingerprint identification are uniqueness and persistence (permanence). To appointment, no ii people have always been found to accept the aforementioned fingerprints—including identical twins. In improver, no single person has ever been found to have the same fingerprint on multiple fingers.

Persistence, also referred to as permanence, is the principle that a person'southward fingerprints remain essentially unchanged throughout their lifetime. Equally new skin cells form, they remain cemented in the existing friction ridge and furrow pattern. In fact, many people accept conducted inquiry that confirms this persistency by recording the same fingerprints over decades and observing that the features remain the aforementioned. Even attempts to remove or damage one'southward fingerprints volition be thwarted when the new skin grows, unless the impairment is extremely deep, in which case, the new organization caused by the damage will at present persist and is also unique.

The Proof is in the Minutiae

Analysts use the general blueprint blazon (loop, ringlet or arch) to make initial comparisons and include or exclude a known fingerprint from further analysis. To match a print, the annotator uses the minutiae, or ridge characteristics, to identify specific points on a suspect fingerprint with the same information in a known fingerprint. For case, an analyst comparing a criminal offense scene print to a print on file would first assemble known prints with the same general blueprint type, and then using a loupe, compare the prints side-by-side to identify specific information inside the minutiae that match. If enough details correlate, the fingerprints are determined to be from the same person.

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