Finger Prints - Forensic Science - Lecture Slides, Slides of Forensics

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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; however, the print itself may

change due to permanent scars and skin diseases.

• Fingerprints have general characteristic ridge patterns

that allow them to be systematically identified.

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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:

60% of people have loops, 35% have whorls,

and 5% have arches

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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. No deltas are present.

Plain Arch Ridges 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”

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Tented Arch

• A tented arch rises sharply

upward causing the center of

the print to look like a tent.

• By definition, the angle of the

lines on a tented arch meets at

less than a 90-degree angle.

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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 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. Docsity.com

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Radial Loops

A radial loop opens toward the

thumb

Print from the right hand

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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 Whorl

Central Pocket Whorl

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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

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It’s time to make

some prints!

Avoid

Partial

Prints

GOOD PRINT Get as much of the top part of your finger as possible! Docsity.com

Directions

1 st^ – 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!

2 nd^ – 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.

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

4 th^ – 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.

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