Fingerprint classification rules

Source: Institute of Applied Science

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FINGERPRINT PATTERN INTERPRETATION


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The naming of any particular pattern is known as pattern interpretation.

Fingerprint classification generally refers to the derived for a complete set of ten fingerprint patterns: Henry with FBI Extensions NCIC


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Three Major Groups

Arches

Loops

Whorls


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Recurving and Converging Ridges

Recurving ridges are ridges that curve back to the direction from which they started

Converging ridges are angles formed by on ridge abutting another ridge

An appendage is a short ridge connects to a recurving ridge at the recurve at a right angle thus is interpreted as ruining the recurve


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Divurging and Bifurcating Ridges

Divurging ridges are ridges which run side by side suddenly separating and flowing in opposite directions.

Bifurcating ridges is when a single ridge splits into two ridges


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Type Lines and Pattern Areas

The pattern area of a fingerprint is that part which lies within the area surrounded by “type lines”

Type lines are the basic boundaries of most fingerprints. Formed by ridges which run parallel from the

lower corners of the pattern and flowing inward and upward toward the edge of the pattern area, where they diverge and separate, then surround or ten to surround the pattern area.


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Whenever the ridge that forms a type line ends suddenly, the next ridge immediately outside of it is taken as its continuation.

The “pattern area” is that part of the fingerprint in which are found the cores, deltas, and other ridges pertaining to a particular pattern type.


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Delta Formations

A “delta” is a point on the first ridge formation at or directly in front of the divergence of the type lines. Sometimes the delta ridge may run into one of

the”type lines”, but the delta can never be located exactly on one of the “type lines”

All bifurcations are not “deltas”, nor are all delta formations “deltas”

To be a “delta”, a bifurcation must be the first ridge formation in front of the divergence of the “type lines”, and the bifurcation must open up toward the pattern area.


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Sometimes the first ridge in front of the divergence will have more than one bifurcation, in such a pattern the bifurcation nearest the core is considered as being the “delta”

Sometimes you will see patterns in which there is a ridge between and parallel to the “type lines” running into the pattern area. The deciding point is the origin of this ridge. If the ridge is wholly located within the pattern

area, the delta is located on the end nearer to the divergence

Should this ridge originate outside the pattern area, the delta is located at the end nearer the core.


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Whenever there is a choice between a bifurcation and some other ridge formation as the location of the delta, the bifurcation is always taken as the delta. EXCEPTION: With one exception the two legs of

the same bifurcation are never “type lines”. The exception occurs when the bifurcation opens toward the core, but is so far outside the pattern area that the legs of the bifurcation run parallel for some distance before they diverge. In such a pattern the legs of the bifurcation are taken as “type lines”.


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REMEMBER THAT TYPE LINES THEMSELVES ARE NEVER CONSIDERED AS THE DELTA, BUT IT IS THE RIDGE FORMATION IN FRONT OF THE DIVERGENCE OF THE TYPED LINES THAT IS THE DELTA.


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Core Formations

The core is the center or the heart of the pattern area.

Cores in loops are formed in a variety of ways, but they are always found either on or within the innermost recurving loop.

A loop pattern may have one single recurving ridge in the center, called a staple or it might have several staples, one inside of another.


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It might have a single ending ridge, in the center of a recurving ridge known as a rod or bar.

When a staple encloses one or more bars it is called an envelope

The are two positions on a recurving ridge known as shoulders. These are on each side of a recurving ridge or

loop where the ridge definitely begins and stops its recurve.


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In patterns in which there is only a single recurving ridge, the core is at the shoulder on the farther side of the loop from the delta.

If the pattern has two or more looping ridges in the core area , that is two staples within each other, without a rod inside the innermost staple, the core is located at the shoulder of the innermost staple on the side farther from the delta.


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When the pattern under consideration shows one rod or bar within the innermost loop ridge, the top of that rod is the core.

Should the innermost loop ridge enclose two bars, the top of the one farther from the delta is the core.

Should an odd number of rods appear within the center of the center-most one is the core.


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Should four or six rods show up with the innermost loop ridge, we consider only the two innermost rods and consider the one farther from the delta as the core.

Should two loops intersect in the center of the pattern area we consider the two recurving ridges within the pattern to be rods and consider the one farthest from the delta to be the core.


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Only those rods which rise to or above the shoulders of the center loop are taken into consideration.


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Loop Patterns

A loop is a pattern in which one or more of the ridges start at one side of the pattern, run toward the upper corner on the opposite side, then recurve and start back toward the side from which they came originally, forming a loop with a core in the center and a delta at the edge of the pattern area.

Loops are the most common fingerprint pattern appearing in 60% of all patterns.

Ulnar loops are more common than radial loops


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To be a loop, a pattern must fulfill four requirements: It must have a core It must have a delta It must have a recurving ridge that passes

between the delta and the core. It must have a ridge count of at least one.


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Ridge Counting

Ridge counting refers to the process of counting ridges that touch an imaginary line drawn between the core and delta of a loop.

The core and delta are NOT counted.


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Radial and Ulnar Loops

There are two types of loops. The Ulnar Loop flows from the little finger

side of the hand and recurves back to that side with the open end pointing in the direction of the little finger

The Radial Loop flows from the thumb side of the hand and recurves back to that side with the open end pointing in the direction of the thumb.

Technology

Fingerprint classification rules