READ: Fingerprints
Classification of Fingerprints
Classification of Fingerprints
Three Fundamental Principles of Fingerprints
1. A fingerprint is an individual characteristic; no two fingerprints have been found to have identical ridge characteristics. This means that even identical twins have different fingerprints!
2. Fingerprints remain unchanged during an individual's lifetime. Injuries such as superficial burns, abrasions, or cuts will not affect the print pattern or alter the dermal papillae. The original pattern will always be duplicated whenever any new skin grows back.
3. Fingerprints have general ridge patterns that permit them to be systematically classified.
Common Types of Fingerprints
There are 3 main patterns of fingerprints; Loop, Whorl and Arch. Some patterns result in a combination of 2 or more of these patterns; these are called "composite patterns". See below for characteristics of fingerprint pattern types.
Characteristics of Fingerprint Pattern Types
|
Pattern Name |
Description |
What % of population has at least one? |
Types |
# of deltas |
|---|---|---|---|---|
|
Loop
|
Ridge lines enter and exit from the same side of the finger.
|
60-65% |
Ulnar Loop: Loop opens toward little finger.
Radial Loop: Loop opens toward thumb.
|
All loops have ONE (1) delta. |
|
Whorl |
Whorls have one ridge line that makes a complete circle around the finger. Also, they have 2 deltas. |
30-35% |
Plain Whorl: Simplest and most common whorl. One complete circuit with spiral or circular shape.
Central Pocket Whorl:Same as plain whorl, but one of the lines curves around a second time.
Double Loop: Two loops combine to make a whorl pattern. It is often also considered a composite pattern. It must have 2 deltas to be considered a type of whorl.
|
All whorls have TWO (2) deltas. |
|
Arch |
A pattern where the ridge lines enter from one side and leave on the opposite side in the shape of an arch. The lines of the pattern lie one on top of the other forming the "arch". |
5% |
Plain Arch: Wave-like pattern where the line enters on one side of the finger, rises subtly in the center like an ocean wave and exits on the other side of the finger.
Tented Arch: Arch pattern with sharp spike at the center of the wave pattern. The spike is shaped like a tent; thus the name! |
No deltas or cores. |
When describing fingerprint patterns, it is important to understand a few basic terms.
Minutiae - Also known as ridge characteristics; minutiae are major features or details of a fingerprint. These details enable examiners to make comparisons of one print with another. Some minutiae found in fingerprints include: bifurcation, core, delta, or island. Minutiae are specifically what make fingerprints individual evidence! Everyone has patterns of loops, whorls or arches in their fingerprints, but the types and placement of minutiae are unique in each person's fingerprints. Typically, 8-16 minutiae point matches identified by a forensic fingerprint expert in a fingerprint is considered a positive match if (and only if) there are NO non-matching minutiae points present! If an additional minutiae point is present in one print that is clearly absent in the other, this automatically becomes a non-match or an exclusion.
Delta - A delta is a minutia pattern within a fingerprint that resembles the Greek letter delta, Δ, and is the result of two diverging lines with the pattern. The two deltas in this whorl pattern have been circled in red.
Core - Center area of a fingerprint. In a whorl, it is the center of the spiral. In a loop, it is a top part of the innermost loop. The core of this Loop fingerprint has been circled.
Types of Fingerprints
Fingerprints can be left on nearly every solid surface; some are easily spotted while others must be coated with powder or viewed under special lighting in order to be seen. A Forensic Scientist has several techniques that can be used to both spot and preserve the three types of fingerprints found in a crime scene. The three types of fingerprints are:
Patent - Fingerprints made after ridges come in contact with a colored material such as blood, dirt, paint or ink. The print is transferred to a surface using the colored material as the "ink". These types of prints are also called visible prints.
Plastic - Fingerprints that are left on a soft material such as soap, clay, wax, or paint. The print is generally three dimensional and remains visible within the soft medium.
Latent (invisible) - Fingerprints are left on a surface as a transfer of body oils and sweat to the surface of an object. They aren't usually seen without the aid of fingerprint powder, reagents or special lighting.
