What are fingerprints?



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Fingerprints Guided Notes Name: ____________________________________

What are fingerprints?

  • Does everyone have a unique fingerprint?



  • How, why, and when do fingerprints develop?



  • Can you alter your fingerprints?

History of Fingerprinting

Fingerprints have served as unique signatures since prehistoric times



  • Early potters & scribes left fingerprints in clay

  • Businessmen in ______________________________________ (8th century AD) used fingerprints on business contracts

Scientific study of fingerprints

  • 1891 ______________________________________

  • 1892 First reported use of fingerprints to solve a crime, in Argentina.

  • 1899 Sir Edward _____________________ developed a way of classifying fingerprints so that investigators could quickly narrow down possible matches.

“Henry system” of classification

Used until computer systems developed



AFIS

  • Automated Fingerprint Identification System

  • Used since 1960s

  • Scans, encodes, and searches fingerprint images

  • After match(es) found, a fingerprint expert evaluates the matches

  • Problem with current system: not all databases linked

Fingerprint Patterns

  • What ARE fingerprints?

    • The fingers, toes, palms of hands, and soles of feet have friction ridge skin made of ridges (raised areas) and furrows (valleys).


Are ridge light or dark? Why?
http://www.griaulebiometrics.com/images/books/understanding/fingerprintformation.bmp

Arches

  • Arches ________________________________________________________________________

______________________________________________________________________________

  • Least common pattern (~5%)

  • Can be ________________ (low rise) or ______________________ (high rise)



Loops

  • Loops _______________________________________________________________

____________________________________________________________________

  • Most common pattern (~65%)

  • Have a _____________________ (the center of the pattern) and a ___________________ (a triangular area)



  • Radial loops open towards the radius of the arm (i.e. towards the thumb).

  • Ulnar loops open towards the ulna of the arm (i.e. towards the pinky)

Whorls

  • Whorls look like “whirlpools”

  • Have a core and two or more deltas

  • _________________________________ are spirals or concentric circles

  • ________________________________ whorls look like a loop with a whirl in the middle

  • ________________________________ have two loops that collide to make an “S” shape

  • ________________________________ are irregular



Types of Fingerprints

  • ____________________________________ - prints that can be seen by the naked eye, made if the finger has touched grease, blood, paint, etc.

  • _____________________________________ – prints that are invisible to the naked eye; formed from natural body oil and perspiration

  • _____________________________________ – 3D negative impression of a fingerprint, made by pressing a finger into a soft, moldable material, such as putty, wax, glue, candy, etc.

Collecting Fingerprints for Evidence

  • ________________ and ________________ prints can often just be photographed for evidence.

  • ____________________________________ must be made visible to be observed & collected.

Visualizing Latent Prints

  1. _________________________________________

    • Most prints (even so-called latent prints) are at least partially visible and can be found by shining a _____________________ or _________________________ source along surfaces _______________________.

    • Used to find prints, especially over large areas

    • UV lights and lasers make fingerprints _______________________, and will reveal more prints than regular flashlights

    • After finding prints with oblique lighting, the prints will need to be further developed (by the methods described next) so that a permanent record can be made)

  2. ________________________________________

    • Can be used to locate (over small areas), enhance, and preserve prints

    • Powder is lightly dusted onto a surface so as not to smear the prints.

    • The powder is ____________________ with ____________________ and put onto ____________________________________.

    • Powders come in a variety of colors, and some are magnetic

  3. ________________________________________

More effective than dusting on porous surfaces, such as paper, leather, styrofoam, etc

  1. ______________________________________

    • Used on ______________ surfaces, including _________________

    • Object is dipped in or sprayed with ninhydrin solution

    • Reacts with amino acids in print

    • Turns purple

  2. _____________________________________

    • Used on _________________ because it is impermanent

    • Evidence is placed in fuming chamber with crystal iodine

    • Iodine is trapped in oils of print to produce brown color

    • Will fade over time

  3. __________________________________________

    • Evidence is placed in a fuming chamber with superglue

    • Heat accelerates the process

    • The glue bonds to the print, forming a ___________, _________________, __________________________________.

    • Superglued prints are usually further treated with chemicals or powders to enhance the visibility of the print.


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