Fingerprints The Fundamentals Every human being carries with him from the cradle to his grave, certain physical marks which do not change their character,

FingerprintsThe Fundamentals

Every human being carries with him from the cradle to his grave, certain physical marks which do not change their character, and by which he can always be identified – and that without shade of doubt or question. These marks are his signature, his physiological autograph, so to speak, and this autograph cannot be counterfeited, nor can he disguise it or hide it away, nor can it become illegible by the wear and mutations of time. - Mark Twain – Pudd’n Head Wilson

Works to Know• Arch• Core• Delta• Fingerprint• Latent fingerprint• Loop• Minutiae• Patent fingerprint• Plastic fingerprint• Ridge pattern• Ten card• Whorl

Why do we have fingerprints?

• Grip better• Makes

perspiration easier on hairless surface

• Improves sense of touch

Fingerprints• Impression made by ridge

patterns on the tip of a finger.• Consists of 98.7% water and

1.3% other substances (amino acids and salt)

• Ridge characteristics start to form around 10 weeks gestation and are fully formed at 14 weeks. Formation due to movement or pressure caused by fetus and mother.

Fingerprint PrinciplesAccording to criminal investigators,

fingerprints follow 3 fundamental principles:

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

a. Determined by ridge patterns called minutiae

b. Average person has 150 individual ridge characteristics on 1 print

Fingerprint Principles2. A fingerprint pattern will remain

unchanged for the life of an individual; however, the print itself may change due to permanent scars and skin diseases.

a. Contains ridges (hills) and

grooves (valleys).

b. Ridges contain pores where perspiration is discharged. This and oils picked up from hair or face are what leaves impressions of prints behind. (latent prints)

Fingerprint Principles3. Fingerprints have general characteristic

ridge patterns that allow them to be systematically identified.

a. ridge characteristics are known as minutiae: ridge endings,

bifurcations, enclosures, and other ridge details.

b. These ridges are placed into 3 classes.

Fingerprint ClassesThere 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 lists below.

ArchPlain arch

Tented arch

LoopRadial LoopUlnar loop

WhorlPlain whorl

Central pocket whorlDouble loop whorl

Accidentical

Interesting Info

Did you know?

Dactyloscopy is the study of fingerprint identification.

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

Fingerprint Factoid: 65% of people have loops,

30 - 35% have whorls, and 5% have arches

ArchesArches are the simplest and least common type of fingerprints that are formed by ridges that enter on one side of the print and exit on the other. No deltas are present.

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”

LoopsLoops 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 Thumb)

Loop opens toward right or the ulna bone.

Radial Loop (Right Thumb)

Loop opens toward the left or the radial bone.

NOTE: On the left hand, a loop that opens to the left would be an ulnar loop, while one that opens to the right would be a radial loop.

WhorlsWhorls 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 Whorl

Central Pocket Whorl

Whorls – Part 2Accidental 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

Identify each fingerprint pattern.

?A B

CD E

Right Hand

Left Hand

Left Hand

Right Hand

Right Hand

It’s time to makesome prints!

Avoid Partial Prints

GOOD PRINTGet as much of the top part of your finger as possible!

Directions

1st – Roll the “pad” portion of your thumb over the ink pad from the left side of your thumb to the right. You do not have to push down really hard!

2nd – Roll the “pad” portion of your thumb from the left side of your thumb to the right in the correct box on your paper to make a thumbprint.

3rd – Continue this process to make a fingerprint of all ten fingers on the “My Prints” worksheet.

4th –Use your notes and a magnifying lens to help you figure out what type of pattern is found in each of your fingerprints. Label each one with the pattern’s name.

Find Your Henry – FBI Number

• The first step to classifying fingerprints is to identify the presence of any whorl patterns.

• A number is assigned based upon what finger the whorl is present.• Add a 1 to the denominator and numerator to avoid zeros.

Right Right Left LeftLeft

Index Ring Thumb Middlelittle

16 8 4 2 1Right Right Right Left

LeftThumb Middle Little Index

Ring16 8 4 2 1

Add a 1 to the numerator and denominator at the end.