Lesson 1- Fingerprint?
What is a fingerprint? What exactly are we referring to when we talk about a fingerprint?
Let me start out by saying that on the palmer surface of person’s hands and on the soles
of his/her feet are raised portions of skin. This is referred to as friction skin. Examine
your own hands closely. Notice this friction skin and its appearance. This friction skin is
what allows us to be able to grip things, such as a glass of water, with ease. It helps us to
hold it firmly. If you examine it more closely, you will see these lines of friction skin
form various shapes and patterns. When the fingertips are coated with a thin layer of ink
and then the finger is pressed onto an object, such as, a fingerprint card, the impression of
these friction ridges is recorded. This recorded image of friction ridges of the tips of the
fingers is the subject of this course.
Interpretation of the various patterns and sub patterns will be discussed in this lesson.
There are three basic fingerprint pattern types. They are:
1. Arch
(Photo)
2. Loop
(Photo)
3. Whorl
(Photo)
These three basic patterns are further sub-classified as follows:
Arches
a. Plain arch
b. Tented arch
Loops
a. Ulnar loop
b. Radial loop
a.
b.
c.
d.
Whorls
Plain whorl
Central pocket loop
Double loop
Accidental
You will need to know the definitions of each of these patterns. Learning the definitions
is essential to the process of classification. These definitions are basically the rules that
govern the way each fingerprint is classified and assures that everyone will classify the
fingerprint the same way. There are rules which govern variances or references, which
will be discussed later.
Definitions
Plain Arch:
A plain arch is that type of pattern in which the ridges enter on one side of the impression
and flow or tend to flow out the other side with a rise or wave in the center.
Tented Arch:
A tented arch is that type of pattern where the ridges enter upon one side of the
impression and flow or tend to flow out upon the other side, as in the plain arch type,
however, the ridge or ridges at the center form and angle, upthrust or possess two of the
three necessary characteristics of a loop.
Loop
A loop is that type of a pattern in which one or more of the ridges enter on either side of
the impression, recurve, touch or pass an imaginary line drawn from the delta to the core,
and terminate or tend to terminate on or toward the same side of the impression from
which they entered.
Whorl
The whorl is that type of pattern in which al least two deltas are present with a recurve in
front of each.
Plain Whorl
The plain whorl has two deltas and at least one ridge making a complete circuit, which
may be spiral, oval, circular, or any variant of a circle. An imaginary line drawn between
the two deltas must touch or cross at least one of the recurving ridges within the inner
pattern area. A recurving ridge, however, which has an appendage connected with it in
the line of flow cannot be construed as a circuit. An appendage connected at that point is
considered to spoil the recurve on that side.
Central Pocket Loop
The central pocket loop type of whorl has two deltas and at least one ridge which makes
or tends to make a complete circuit. The circuit may be spiral, oval, circular, or any
variant of a circle. An imaginary lime drawn between the two deltas must not touch or
cross any recurving ridges within the inner pattern area. A recurving ridge, however,
which has an appendage connected with it in the line of flow and on the delta side cannot
be construed as a circuit. An appendage connected at that point is considered to spoil the
recurve on that side.
In lieu of a recurve in front of the delta in the inner pattern area, an obstruction at right
angles to the line of flow will suffice.
Double Loop
The double loop type whorl consists of two separate loop formations, with two separate
and distinct sets of shoulders, and two deltas.
Accidental
The accidental whorl is a pattern consisting of a combination of two different types of
patterns, with the exception of the plain arch, with two or more deltas; or a pattern which
possesses some of the requirements for two or more different types; or a pattern which
conforms to none of the definitions.