Semester 1 Honors Forensic Science Test Study Guide Unit 3 part...
Transcript of Semester 1 Honors Forensic Science Test Study Guide Unit 3 part...
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
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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