Topic 4 Study Guide-Fingerprints PDF

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Physical evidence...

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SCI 330 Topic 4 Study Guide: Fingerprint Evidence History 

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Alphonse Bertillon - Was a French police expert, developed a system that stored a detailed description of the suspect. (Mugshots) Francis Galton - Discussed the anatomy of fingerprints, no two fingerprints are identical. Adoption of fingerprints - Bertillon

Fundamental principles of fingerprints 

Principle #1: Individual characteristics o ridge characteristics--understand how they contribute to individuality & be able to identify them o Loops, Arches, and Whorls o Type, number, and location  Characteristics must be identical  Characteristics must be in the same relative location  Point by point comparison o ridge comparisons o All nine identifications of the fingerprint         

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Delta Ridge ending Bifurcation Island Core Crossover Pore Hook Eye

Principle #2 o Skin structure o Epidermis is the outer layer o Dermis is the inner layer o Dermal Papillae the section in between that forms the friction ridges o Contains a single row of pores leading to sweat gland. o changes/alterations to fingerprints o It is impossible to eliminate all characteristics of a fingerprint

SCI 330 Topic 4 Study Guide: Fingerprint Evidence

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o If an injury reaches the dermal papillae a permanent scar will form which alters the fingerprint. Principle #3 o General ridge patterns--be able to identify o Loops 60-65% have this pattern (Most popular)  Loops toward the pinky are ulnar loops  Loops toward the thumb are radial loops o Whorls 30- 35% have this pattern (Second Popular)  Have at least 2 deltas  Four types  If line doesn’t touch the spiral ridges, then it’s a Central pocket loop  If line touches spiral ridges its Plain whorl.  Accidental  Double (Twin) Loop o Arches 5% rare pattern  Simplest of the patterns  Ridges enter from one side and exit the other  There are no deltas  Two general types  Tented arch has a sharp thrust  Plain arch rises smoothly in the center

AFIS 

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How AFIS searches are performed o Two different types of searches  Pattern based  Minutae- based Understand how final conclusion is reached when AFIS is used o Why it must be done this way  Computer can’t be adequate to arrive to a conclusion  An examiner gives the final conclusion

The Madrid Bombing 

Purpose for the misidentification o They were pressured in arriving to a conclusion and tried to be the first.

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How it changed the number of matching minutae needed for ID

SCI 330 Topic 4 Study Guide: Fingerprint Evidence o Eight is the minimum since 7 was as much as they used. Detecting prints 

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three types of prints found at scenes o Visible Prints  Prints in blood or paint o Plastic Prints  Ridges left on soft material like wax o Invisible Prints  Transfer of sweat and oil onto a surface how fingerprints are located o Hard nonabsorbent surfaces require powders o Soft porous surfaces use chemical treatments porous vs nonporous surfaces o UV Lights on nonabsorbent surfaces developing fingerprints using o powders o will adhere to sweat and oils o Black and Gray best contrast for examination o Magnetic and Powder o iodine fuming o Oldest chemical method o Heated iodine crystals create a vapor o Ninhydrin o Sprayed on a porous surface o Can be heated to speed up reaction o Reacts with amino acids in sweat o super glue fuming (cyanoacrylate) o Used for nonporous surfaces o Uses cyanoacrylate ester fumes adheres to prints o Add superglue to a cotton ball and add sodium hydroxide o fluorescence o laser and ALS

Preserving developed prints 

When they should be collected on scene o Best way to collect at the scene

SCI 330 Topic 4 Study Guide: Fingerprint Evidence Enhancing developed prints How fingers and fingerprints are made ACE-V  

Define the acronym & what’s done at each step Three levels of detail o What’s examined at each level o What’s needed to make an ID

Biometrics   

Why biometrics is hard 4 steps completed by all devices Hand geometry o Advantages o Disadvantages o How it works

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Fingerprints o Advantages o Disadvantages o Style of acquisition o How it works...