Semester 1 Honors Forensic Science Test Study Guide Unit 3 part 1: Fingerprinting

1 Made by Ashley Thomas Source

– What are fingerprints?

ᴑ A raised area on the surface of the skin that aids in grip utilizing friction

ᴑ We leave fingerprint patterns behind due to secretions from our skin (oil, sweat, dirt, water)

– Begin developing in womb at 10 weeks into pregnancy but aren’t set until 24 weeks into pregnancy

– Ridges are so deep that they cannot be altered

ᴑ People have tried burning them off, filing them away, and using acid from pineapples to remove

them but nothing works

– Types of prints

ᴑ Plain arch

Ridges enter on one side and exit on the other

Small rise in center

ᴑ Tented arch

Ridges enter on one side and exit on the other

Sharp spike in the middle (looks like a tent or a delta)

ᴑ Ulnar and Radial Loops

Loops: ridges enter and exit on the same side of the print

Radial: delta on the side of the fingerprint that is closer to the thumb on the given hand

Right Hand: Delta on right

Left Hand: Delta on left

Ulnar: delta on the side of the fingerprint that is closer to the pinky on the given hand

Right Hand: Delta on Left

Left Hand: Delta on Right

ᴑ Plain Whorl

Ridges make a complete circuit between two deltas

ᴑ Double Loop Whorl

Two loops combined together

ᴑ Central Pocket Whorl

Looks “wackier” than plain whorl

No complete circuit between the two deltas

ᴑ Accidental Whorl

Combination of more than one pattern

Exceedingly unusual

Diagrams on next page

Semester 1 Honors Forensic Science Test Study Guide Unit 3 part 1: Fingerprinting

2 Made by Ashley Thomas Source

ᴑ The general type of pattern (any of the 8 above) are considered class evidence, minutiae

(discussed later) are what makes the fingerprint a form of individual evidence

ᴑ Statistics

Loop: 60-65% of the population

Semester 1 Honors Forensic Science Test Study Guide Unit 3 part 1: Fingerprinting

3 Made by Ashley Thomas Source

Whorl: 30-35% of the population

Arch: 5% of the population

– AFIS: Automated Fingerprint Identification System

ᴑ Utilizes computers to mark minutiae and leave a unique pattern instead of just an unmarked

fingerprint

ᴑ Normally a person will go back through and make sure the system didn’t miss anything

Specialists can label what the minutiae are (what type), whereas the computer just

identifies where they are

ᴑ 27 Minute process

ᴑ 10-16 Minutiae are the same = Matching Print

– Kinds of crime scene prints

ᴑ Best way to preserve prints is PHOTOGRAPHY

ᴑ Visible Prints

Touch surfaces after ridges were in contact with something colored

Blood, paint, ink

ᴑ Plastic Prints

Ridges left impression in a soft material

Soap, putty, wax

ᴑ Latent Prints

Invisible

Caused by perspiration on ridges

Sweat, oil, water, salt, amino acids

– Collection Methods

ᴑ Carbon Powder

Lightly dust surface

Print turns BLACK

Use on light or invisible fingerprints (Latent usually)

Only used on non-porous surfaces (metals, drywall, concrete, countertop)

Sticks to oil in fingerprints lift with sticky tape

ᴑ Ninhydran

Used on porous surfaces

Dip or spray solution onto fingerprint, then wait 24 hours for the amino acids to react with

the solution

Print turns BLUE/PURPLE

ᴑ Cyanoacrylate Vape (Superglue Fumigation)

Household materials (small objects)

Knife, spatula, spoon, pan, pen

Put cyanoacrylate in vapor tent with object, heat, wait for amino acids to react with solution

Prints turn WHITE

– Primary Classification

ᴑ Based off on number of whorls

ᴑ DO NOT SIMPLIFY THE FRACTION

ᴑ Formula: 𝑅𝑖𝑛𝑑𝑒𝑥+𝑅𝑟𝑖𝑛𝑔+𝐿𝑡ℎ𝑢𝑚𝑏+𝐿𝑚𝑖𝑑𝑑𝑙𝑒+𝐿𝑙𝑖𝑡𝑡𝑙𝑒+1

𝑅𝑡ℎ𝑢𝑚𝑏+𝑅𝑚𝑖𝑑𝑑𝑙𝑒+𝑅𝑙𝑖𝑡𝑡𝑙𝑒+𝐿𝑖𝑛𝑑𝑒𝑥+𝐿𝑟𝑖𝑛𝑔+1

Semester 1 Honors Forensic Science Test Study Guide Unit 3 part 1: Fingerprinting

4 Made by Ashley Thomas Source

Right Index/ Right Thumb = 16

Right Ring/ Right Middle = 8

Left Thumb/ Right Little = 4

Left Middle/ Left Index = 2

Left Little/ Left Ring = 1

– Minutiae