Chapter 6 Fingerprints

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Chapter 6 Fingerprints

• Fingerprints cannot lie, but liars can make
  fingerprints.
• Unknown

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Historical Development

• The oldest known documents showing fingerprints
  date from third century B.C. China.
• In ancient Babylon (1792-1750 B.C.), fingerprints
  pressed into clay tablets marked contracts.
• In 1788, Johann Mayer noted that the arrangement
  of skin ridges is never duplicated in two
  persons. He was probably the first scientist to
  recognize this fact.

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Historical Development

• 4. Sir William Herschel (shown top right), in
  1856, began the collection of fingerprints and
  noted they were not altered by age.
• 5. In 1888, Sir Francis Galton (shown bottom
  right), and Sir Edmund Richard Henry, developed
  the fingerprint classification system that is
  still in use in the United States.
• By 1896, all ten fingerprints were imprinted on a
  card (called a ten card) of any convicted
  criminals.
• What major problem still existed that is
  significantly improved today?

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What Are Fingerprints?

• All fingers, toes, feet, and palms are covered in
  small ridges.
• Natural secretions (mostly water from sweat
  glands!) plus dirt on these surfaces leave behind
  an impression (a fingerprint).

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Fingerprints

• The ridges are arranged in connected units called
  dermal (or friction) ridges.
• These ridges and the hundreds of sweat pores on
  our fingertips help us grip objects.
• Any time you touch something a fingerprint is
  left behind.

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Because the surface area of friction ridges on
geckos feet is so dense, they can walk on
vertical glass.
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Formation of Fingerprints

• The creation of fingerprints occurs in a special
  layer (the basal layer) in the epidermis where
  new skin cells are produced.
• The basal layer is the innermost layer of the
  epidermis.
• Fingerprints probably begin forming at the start
  of the 10th week of pregnancy when the fetus is
  about 3 inches long.
• Because the basal layer grows faster than the
  others, it collapses, forming intricate shapes.

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Basal Layer
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Characteristics of Fingerprints

• There are 3 general fingerprint distinctions
• ARCH WHORL LOOP
• About 5 About 30
  About 65 of the population

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Characteristics of Fingerprints

• Forensic examiners look for the presence of a
• core - center of whorl or loop
• deltas - triangular regions near a loop
• ridge count - the number of ridges from the
  center of the core to the edge of the delta (p.
  137)

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Characteristics of Fingerprints

• Basic patterns can be further divided (p. 138)
• Arch patterns can be
• Plain Arch (4)
• Tented Arch (1) forms an angle with a delta
• Whorl patterns can be
• Central Pocket (2)
• Double Loop (4)
• Accidental (0.01)
• Even twins have unique fingerprints due to small
  differences (called minutiae) in the ridge
  patterns.

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Types of Fingerprints

• There are 3 types of prints that investigators
• look for at crime scenes
• Patent fingerprints are visible prints
  transferred onto smooth surfaces by blood or
  other liquids.
• Plastic fingerprints are indentations left in
  soft materials such as clay or wax.
• Latent fingerprints are not visible but made so
  by dusting with powders or the use of chemicals.

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What type and where can prints be recovered at
this scene?
A local pottery studio was robbed while the
potter was out. The thieves broke a window on
the studios front door and then reached inside
the broken window, turning the doorknob to get
in. Designs the potter had drawn for her future
creations were strewn about the room. A fresh
clay platter was torn in half. A cash register
was forcibly opened and all of the cash was
taken. The criminals left by simply opening the
back door.
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Latent Plastic
A local pottery studio was robbed while the
potter was out. The thieves broke a window on the
studios front door and then reached inside the
broken window, turning the doorknob to get in.
Designs the potter had drawn for her future
creations were strewn about the room. A fresh
clay platter was torn in half. A cash register
was forcibly opened and all of the cash was
taken. The criminals left by simply opening the
back door.
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Fingerprint Forensic FAQs

• Can fingerprints be altered?
• No, if, for example, they are removed with
  chemicals, they will grow back.
• Is fingerprint identification reliable?
• Yes, but analysts can make mistakes.
• Is fingerprint matching carried out by computers
  in a matter of seconds?
• No, but the FBIs Integrated Automated
  Fingerprint Identification System (IAFIS or AFIS)
  can provide a match in 2 hours for the prints in
  its Master File.

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Fingerprint Forensic FAQs

• How are latent fingerprints collected?

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The Future of Fingerprinting

• New scanning technologies and digitally
  identifying patterns may eliminate analytical
  mistakes.
• Trace elements of objects that have been touched
  are being studied to help with the identification
  of individuals.
• To help with identification, other physical
  features such as eyes and facial patterns are
  also being studied.
• http//school.cengage.com/forensicscience/home.htm
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