Fingerprints

DactyloscopyThe Study of Fingerprints

Kendall/Hunt Publishing Company

3Recording and classifying prints

Rolling inked prints

Loops, whorls, arches, ridge characteristics

Primary identification number

Lifting prints

Black, white, and fluorescent powder

Chemicals—ninhydrin, iodine, silver nitrate, cyanoacrylate

Other types of prints

Palm, lip, teeth, eye, ear, voice, shoeprints, and footprints

Fingerprint Principles

According to criminal investigators, fingerprints follow 3 fundamental principles:

A fingerprint is an individual characteristic; no two people have been found with the exact same fingerprint pattern.

A fingerprint pattern will remain unchanged for the life of an individual.

Fingerprints have general characteristic ridge patterns that allow them to be systematically identified.

Fingerprint Classes

There are 3 specific classes for all fingerprints based upon their visual pattern: arches, loops, and whorls.

Each group is divided into smaller groups as seen in the list below.

ArchPlain arch

Tented arch

LoopRadial LoopUlnar loop

WhorlPlain whorl

Central pocket loopDouble loopAccidentical

Interesting Info

Fingerprint Fact:

65% of people have loops, 30% have whorls,

and 5% have arches

Did you know?

Police investigators are experts in collecting “dactylograms”, otherwise known as fingerprints.

Arches

Arches are the simplest type of fingerprints that are formed by ridges that enter on one side of the print and exit on the other.

Plain ArchRidges enter on one side and

exit on the other side.

Tented Arches Similar to the plain arch,

but has a spike in the center.

Spike or “tent”

Loops

Loops must have one delta and one or more ridges that enter and leave on the same side. These patterns are named for their positions related to the radius and ulna bones.

Delta

Ulnar Loop (Right Hand)Loop opens toward the little finger (or ulna).

Radial Loop (Right Hand)Loop opens toward the thumb (or radius).

Delta

Whorls

Whorls have at least one ridge that makes (or tends to make) a complete circuit. They also have at least two deltas. If a print has more than two deltas, it is most likely an accidental.

Draw a line between the two deltas in the plain and central pocket whorls. If some of the curved ridges touch the line, it is a plain whorl. If none of the center core touches the line, it is a central pocket whorl.

Plain WhorlCentral Pocket Whorl

Whorls – Part 2

Accidental Whorl

Accidental whorls contain two or more patterns (not including the plain arch), or does not clearly fall under any of the other categories.

Double Loop Whorl

Double loop whorls are made up of any two loops combined into one print.

Delta

Delta

Ridgeology

Ridgeology: The study of the uniqueness of friction ridge structures and their use for personal identification.

The term “ridgeology” was coined by Sergeant David Ashbaugh to describe the scientific evaluation process used for friction ridge identifications.

As we have learned in our first lesson, a fingerprint is made of a series of ridges and valleys on the surface of the finger. The uniqueness of a fingerprint can be determined by the pattern of ridges and valleys as well as the location, shape, and position of minutiae points, which are points where the ridge structure changes.

Image from http://www.cs.usyd.edu.au/~irena/minutia.gif

Did You Know?????

The koala is one of the few mammals (other than primates) that has fingerprints. In fact, koala fingerprints are remarkably similar to human fingerprints; even with an electron microscope, it can be quite difficult to distinguish between them.

4. Ridge Characteristics

5. Take a look at the sample fingerprint below to see several ridge characteristics that you might find during a fingerprint examination.

Crossover

Core

Bifurcation (fork)

Ridge ending

Island

Delta

Pore

Scar

6. How many ridge characteristics can you identify in this fingerprint?

Automated Fingerprint Identification System (AFIS)

AFIS is a computerized system capable of reading, classifying, matching, and storing fingerprints for criminal justice agencies. Quality latent fingerprints are entered into the AFIS for a search for possible matches against the state maintained databases for fingerprint records to help establish the identity of unknown deceased persons or suspects in a criminal case.

http://www.fdle.state.fl.us/CrimeLab/images/fingerrint%20comparison%20for%20afis.jpg

When minutiae on two different prints match, these are called points of similarity or points of identification.

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Fingerprint Identification

For almost a hundred years, the primary method used to examine prints was the point system. An examiner would compare the ridges in two prints, and if enough of the ridge points matched, anywhere from twelve to sixteen, then there was said to be an identification.

Fingerprints cont.

In the past ten years, there has been a shift away from the points system to the system known as “ridgeology”.1 An examiner must determine if there are enough features (not just points) in common to determine if two fingerprints are matches.

Possible features to consider in identification: Overall ridge pattern Individual ridge patterns (ridge ending, bifurcation, dot, etc.) Individual ridge structures (width, shape, position of pores, etc.) Other features present in a print, such as creases, scars, warts, etc.

Quick Tips

It’s time to take some prints!

Latent prints are impressions left by friction ridge skin on a surface, such as a tool handle, glass, door, etc.

Prints may be collected by revealing them with a dusting of black powder and then lifted with a piece of clear tape.

Did you know?

Did you know? Camel hair is the most common animal hair used to make fingerprint brushes. Now many brushes (like the one above) are made out of fiberglass.

Latent Prints

Some investigators use fluorescent powder and UV lights to help them find latent prints on multi-colored or dark surfaces.

Magnetic powder can also be used to reveal latent prints. This type of powder works better on shiny surfaces or plastic baggies or containers.

Latent Prints

The cyanoacrylate fuming method (often called the super glue method) is a procedure that is used to develop latent fingerprints on a variety of objects.