Fingerprinting

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Fingerprinting

• By Melissa Chang

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Fingerprinting Introduction
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What Is a Fingerprint?

• The skin on our fingers are made up of many
  ridges of skin that are created when we are still
  in our mothers womb. They remain the same for
  the rest of our lives, even surviving injury if
  not too severe. Each of the ridges connect to
  other ridges, forming a pattern that is unique to
  all others. No two people in the world have
  exactly the same print. This uniqueness is used
  in many forensic cases to solve crimes, as some
  of the most common evidence found at a crime
  scene are fingerprints.

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• The way a suspect print is analyzed is that its
  compared to a print found at a crime scene. If
  there are a certain number of points of minutiae
  that match, then a match is made.
• Minutiae are small details that are breaks in the
  patterns of the ridges. No two people have the
  same set of minutiae.

Examples of types of minutiae from
perso.orange.fr/.../types/fingerprint.htm
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Print Types

• Latent prints- latent prints are hidden and
  deposited via the secretions from skin. They are
  often made visible through a number of different
  techniques.
• Patent prints- highly visible and made from
  foreign substances such as blood. Since they need
  no further visualization, they are often just
  photographed to preserve the evidence.
• Plastic prints- Friction ridge impressions
  deposited in a material that retains the shape
  such as clay or or melted wax.

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Classification

• Arches
• Whorls

• Loops

The most commonly found types of fingerprints are
whorls, while the least common types are arches.
Loops fall somewhere inbetween.
There is more specific types of classification
techniques, and these are just the most basic
three. For example, arches can be broken down
into plain arches or tented arches, and whorls
can be broken down into accidental whorls, or any
other number of whorl types.
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PC system (Primary Classification)

• The primary classification system is a system
  concerning the whorl patterns in the
  fingerprints. Everyone is assigned a pc value
  according to the whorls on their fingers. This
  system is not used for identification, but for
  narrowing the pool of candidates.

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The History of Fingerprinting
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• Fingerprinting has its roots in the early
  1800s when a professor of anatomy at the
  University of Breslau first wrote a paper
  discussing fingerprint patterns. However, it
  wasnt until years later when a man by the name
  of Francis Galton published a book discussing the
  matter that it was used to identify individual
  persons.

Sir Francis Galton
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Timeline

• 1823 Jan Purkyne publishes thesis on fingerprint
  patterns.
• 1880 Dr. Henry Faulds publishes his article on
  the subject in a science magazine and offers his
  ideas to the London police. The idea is rejected.
• 1892 Sir Francis Galton publishes a statistical
  model of fingerprint analysis and discusses his
  theory that it could be used in forensic science.
• 1892 An Argentine police officer makes the first
  criminal fingerprint identification in a murder
  case.
• 1901 The UK Fingerprint Bureau is created in
  Scotland Yard.

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Techniques For Lifting a Print
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Dusting

• Used on smooth, non-porous materials.
• The area is lightly and carefully dusted with
  either a black or white powder, depending on the
  contrasting surface.
• The dust is lifted with tape and set against a
  contrasting background.
• The print is preserved via photography.

Fingerprint dusting in a lab
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Iodine Fuming

• Suspect material is placed in an enclosed
  cabinate along with iodine crystals.
• The crystals are heated, and will sublimate (turn
  into a gas vapor).
• The vapors cause the prints to visualize.

Fingerprint visualized with iodine fuming.
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Chemical Treatment

• Ninhydrin (triketohydrindene hydrate)- this
  chemical is sprayed onto a porous surface via an
  aerosol can. Prints begin to visualize an hour or
  two after application, although the process can
  be accelerated through heating the print.
• Silver nitrate- silver nitrate is sprayed onto
  the porous surface and left to dry. Then it is
  exposed to ultraviolet light to visualize the
  prints.

Silver Nitrate spray bottle
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Superglue Fuming

• Used mainly on non-porous materials.
• Superglue is placed on cotton and treated with
  sodium hydroxide.
• Fumes can also be created by heating the glue.
• The fumes and the object are contained in a
  closed chamber for up to six hours.
• The fumes adhere to the print, visualizing it.

Fuming tank
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Analysis of Prints
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• As mentioned before, prints are analyzed by
  looking for points of interest or minutiae.
• If 8-16 match points are made, the fingerprints
  match.
• Nowadays a computer can be used to assist this
  process of matching points.
• Known criminals are fingerprinted, and the prints
  are filed away in a database known as the
  Integrated Automated Fingerprint Identification
  System. If a print is found at a crime scene,
  investigators look for a match in the database.

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Minutiae Types

• ridge endings - a ridge that ends abruptly
• ridge bifurcation - a single ridge that divides
  into two ridges
• short ridges, island or independent ridge - a
  ridge that commences, travels a short distance
  and then ends
• ridge enclosures - a single ridge that bifurcates
  and reunites shortly afterward to continue as a
  single ridge
• spur - a bifurcation with a short ridge branching
  off a longer ridge
• crossover or bridge - a short ridge that runs
  between two parallel ridges

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Fingerprinting Today
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• Fingerprinting is widely used to identify
  criminals today.
• The Integrated Automated Fingerprint
  Identification System (IAFIS) is widely used to
  keep track of known criminals.
• New methods of visualizing prints, such as
  lasering, are being developed.

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Brain Fingerprinting

• Brain fingerprinting is a technique used to
  measure the recognition of familiar sights by
  measuring brain wave responses to sights, words,
  or phrases that are set before a person. This
  response is known as a MERMER (Memory and
  Encoding Related Multifaceted Electroencephalograp
  hic Response)
• It was developed by Dr. Lawrence Farwell, and has
  been used lately in many different cases.

Taken from seattlepi.nwsource.com/local/162685_bra
in01.html