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Fingerprinting - PowerPoint PPT Presentation

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Fingerprinting. By Melissa Chang. Fingerprinting: Introduction. What Is a Fingerprint?.

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By Melissa Chang

what is a fingerprint
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 mother’s 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.

The way a suspect print is analyzed is that it’s 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

print types
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.
  • 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.

pc system primary classification
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.

Fingerprinting has it’s roots in the early 1800s when a professor of anatomy at the University of Breslau first wrote a paper discussing fingerprint patterns. However, it wasn’t 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

  • 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.
  • 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

iodine fuming
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.

chemical treatment
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

superglue fuming
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

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.
minutiae types
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
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.
brain fingerprinting
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 Electroencephalographic Response)
  • It was developed by Dr. Lawrence Farwell, and has been used lately in many different cases.

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