Forensics U3: Fingerprints
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What are the fundamental principles of fingerprints?
• Unique characteristics make them individual evidence • Consistent over a person’s lifetime • Systematically classified
Describe the formation of fingerprints
Ridges and Valleys
The purpose of fingerprints is to…
link a portion of a crime scene to an individual.
Prints are also found:
Using the AFIS (Automated Fingerprint Identification System)
Fingerprints cannot be removed because…
the ridges of skin that create a fingerprint run deep.
Fingerprinting is __________ evidence, meaning it puts you ___ ___ ________ ______.
physical at the crime scene
Describe the use of fingerprints in investigations.
Comparing fingerprints found at a crime scene and linking them back to the shared fingerprint owner.
Ridgeology
The study of the uniqueness of friction ridge structures and their use for personal identification.
A fingerprint is made of a series of _______ ____ ________.
ridges and furrows
The uniqueness of a fingerprint can be determined by ____ _________ of ridges and valleys as well as the ____________ _________, which are points where the ridge structure changes.
the pattern minutiae points
Describe the importance of identifying minutiae in a case.
Used to determine the uniqueness of a fingerprint image.
How many points of similarity do the US and international courts accept for a match?
8 out of 12
Describe AFIS (Automated Fingerprint Identification System) and its importance.
Stores and retrieves fingerprints, the AFIS searches files for a set of prints and compares a single print from a crime scene.
AFIS
Automated Fingerprint Identification System
Other than fingerprints, describe other prints that are accurate in linking a suspect to a crime scene.
Palm Lip Voice Shoe Foot Eye Teeth
Describe the importance of a latent print.
It can link a suspect to a crime scene. Provide proof of contact. Identify people that may not previously have been known.
Describe the type of print development listed below: Powders/dusting
Adheres to both water and fatty deposits, Choose a color to contrast with the background, Best on hard, nonabsorbent surfaces, Develop print by “lifting” with clear sticky tape.
Describe the type of print development listed below: Iodine
Fumes react with oils and fats to produce a temporary (short lasting) yellow-brown colored print, Works best on porous paper.
Describe the type of print development listed below: Ninydrin
Reacts with amino acids to produce an orange to purple color, Best with paper, tissue, clothing and other porous surface.
Describe the type of print development listed below: Silver Nitrate
Reacts with chloride in salt to form silver chloride, This will turn into silver oxide (gray) when exposed to light, Best for porous substances like paper and drywall.
Describe the type of print development listed below: Cyanoacrylate
Superglue fumes react with water and other fingerprint constituents to form a hard, whitish deposit , This can then be treated with powders or fluorescent dyes to make a sharper contrast for photos or lifting.