Fingerprint 101

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Fingerprint 101 Powered By Docstoc
					T. Trimpe 2006 & Bertino
                   A Brief History

• Early 1800s—fingerprint
  patterns first discussed
• 1892—Francis Galton
  published book fingerprints
  used to identify individual

                                     Sir Francis Galton
           What Is a Fingerprint?
• Ridges of skin that are created when we
  are still in our mother’s womb.
• Remain the same for the rest of our lives
• Each of the ridges connect to other
  ridges, forming a pattern that is unique to
  all others.

• 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.
       Fingerprint Principles
According to criminal investigators, fingerprints follow
  3 fundamental principles:
• A fingerprint is an individual characteristic; no two
  people have been found with the exact same
  fingerprint pattern.
• A fingerprint pattern will remain unchanged for the
  life of an individual; however, the print itself may
  change due to permanent scars and skin diseases.
• Fingerprints have general characteristic ridge patterns
  that allow them to be systematically identified.
        Fingerprint Classes
There are 3 specific classes for all fingerprints based
upon their visual pattern: arches, loops, and whorls.

         Each group is divided into smaller groups
                as seen in the lists below.

     Arch           Loop                Whorl
   Plain arch    Radial Loop         Plain whorl
  Tented arch    Ulnar loop      Central pocket whorl
                                  Double loop whorl
             Interesting Info
          Fingerprint Factoid:
60% of people have loops, 35% have whorls,
           and 5% have arches

                  Did you know?
Dactyloscopy is the study of fingerprint identification.
     Police investigators are experts in collecting
   “dactylograms”, otherwise known as fingerprints.
Arches are the simplest type of fingerprints that are formed by
ridges that enter on one side of the print and exit on the other. No
deltas are present.
                                                     Spike or “tent”

            Plain Arch                     Tented Arches
   Ridges enter on one side and        Similar to the plain arch,
      exit on the other side.         but has a spike in the center.
Loops must have one delta and one or more ridges that enter and
leave on the same side. These patterns are named for their positions
related to the radius and ulna bones.


      Ulnar Loop (Right                        Radial Loop (Right
            Thumb)                                    Thumb)
       Loop opens toward                      Loop opens toward the
     right or the ulna bone.                  left or the radial bone.

 NOTE: On the left hand, a loop that opens to the left would be an ulnar
    loop, while one that opens to the right would be a radial loop.
Whorls have at least one ridge that makes (or tends to make) a
complete circuit. They also have at least two deltas. If a print has
more than two deltas, it is most likely an accidental.


Draw a line between the two deltas in the plain and central pocket
whorls. If some of the curved ridges touch the line, it is a plain
whorl. If none of the center core touches the line, it is a central
pocket whorl.
                Whorls – Part 2
        Double Loop Whorl       Accidental Whorl



Double loop whorls are      Accidental whorls contain two
made up of any two loops    or    more      patterns   (not
combined into one print.    including the plain arch), or
                            does not clearly fall under any
                            of the other categories.
    Identify each fingerprint pattern.

Left Hand                         Right Hand

                  Right Hand

  Right Hand                    Left Hand
Ridgeology: The study of the uniqueness of friction ridge structures
and their use for personal identification.1

As we have learned in our first lesson, a
fingerprint is made of a series of ridges and
valleys on the surface of the finger. The
uniqueness of a fingerprint can be determined by
the pattern of ridges and valleys as well as the
minutiae points, which are points where the ridge
structure changes.

                               The koala is one of the few mammals (other than primates) that
                               has fingerprints. In fact, koala fingerprints are remarkably
                               similar to human fingerprints; even with an electron microscope,
                               it can be quite difficult to distinguish between the two.

 1Introduction   to Basic Ridgeology by David Ashbaugh, May 1999   Image from
Fingerprint Identification
When minutiae on two different prints match, these are called
points of similarity or points of identification. At this point there
is no international standard for the number of points of
identification required for a match between two fingerprints.
However, the United Kingdom requires a minimum sixteen points
while Australia requires twelve.

       Automated Fingerprint Identification System (AFIS)
                                                                                       AFIS is a computerized system capable of
                                                                                       reading, classifying, matching, and storing
                                                                                       fingerprints for criminal justice agencies. Quality
                                                                                       latent fingerprints are entered into the AFIS for a
                                                                                       search for possible matches against the state
                                                                                       maintained databases for fingerprint records to
                                                                                       help establish the identity of unknown deceased
                                                                                       persons or suspects in a criminal case.
  Ridge Characteristics

Use these characteristics as points of identification when comparing fingerprint
samples. The more points you can find in common, the better the match!
      Ridge Characteristics



                                                              Bifurcation (fork)

                                                              Ridge ending
r                                                             Island


How many ridge characteristics can you identify in this fingerprint?

  Try It!
1 – Blow up your balloon about halfway and twist the end to keep the
air from coming out. Do not tie it off!
2 – Use an ink pad to make a print with all of your fingers and label each
one with a permanent marker. Write your name on the balloon as well.
3 – Blow up the balloon to full size and tie the end.
4 – Analyze the fingerprints to find several ridge structures that we have
discussed. Use a highlighter to mark these structures on your “My
Prints” worksheet.

      Think About It!
      Which ridge structures were most common in your fingerprints?
      Which ridge structures were most common in your group?
      Were there any structures that were not found in any of the fingerprints?
  Balloon Fingerprint Activity:
              Analyzing Prints
• 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         Examples of types of minutiae from
  details that are breaks
  in the patterns of the                       m

  ridges. No two people
  have the same set of
                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
• 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.
     Classification Review
• Arches   • Loops
                                The most commonly found types
                                of fingerprints are whorls, while
                                the least common types are
                                arches. Loops fall somewhere

• Whorls   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.
 It’s time to make
    some prints!

                      GOOD PRINT
Prints               Get as much of the top part
                     of your finger as possible!
Ten Card Example
1st – Roll the “pad” portion of your thumb over the
ink pad from the left side of your thumb to the
right. You do not have to push down really hard!

2nd – Roll the “pad” portion of your thumb from the left side of
your thumb to the right in the correct box on your paper to make a

3rd – Continue this process to make a fingerprint of all ten fingers
on the “My Prints” worksheet.

4th –Use your notes and a magnifying lens to help you figure out
what type of pattern is found in each of your fingerprints. Label
each one with the pattern’s name.
      What Are Fingerprints?
• All fingers, toes, feet, and palms are
  covered in small ridges
• Ridges help us grip objects
• Ridges are arranged in connected units
  called dermal, or friction, ridges
• Fingers accumulate natural secretions
  and dirt
• Fingers leave create prints on objects we
Structure of Skin

Techniques For Lifting a
• 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.    Fingerprint dusting in a lab
• The print is preserved
  via photography.
             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).         Fingerprint visualized with
                                  iodine fuming.
• The vapors cause the
  prints to visualize.
             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
• 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
           Superglue Fuming
• Used mainly on non-porous
• 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
     Fingerprint Forensic FAQs

• Can fingerprints be erased?
  Only temporarily; they will grow back if removed with chemicals

• Is fingerprint identification reliable?
  Yes, but analysts can make mistakes

• Can computers perform matches in
  No, but the FBI’s Integrated Automated Fingerprint Identification
  System (IAFIS or AFIS) can provide a match in 2 hours

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