Transcript Fingerprint

Forensic Science
T. Trimpe 2006 http://sciencespot.net
Fingerprint Principles
According to criminal investigators, fingerprints follow 3
fundamental principles:
1. A fingerprint is an individual characteristic; no two
people have been found with the exact same fingerprint
pattern.
2. 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.
3. 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
Plain arch
Tented arch
Loop
Radial Loop
Ulnar loop
Whorl
Plain whorl
Central pocket whorl
Double loop whorl
Accidentical
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
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
Ridges enter on one side and
exit on the other side.
Tented Arches
Similar to the plain arch,
but has a spike in the center.
Left
Hand
Loops
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, i.e. the
bone the loop opening is facing towards.
Ulna
Radius
Delta
L – Radial Loop
R - Ulnar Loop
L – Ulnar Loop
R - Radial Loop
X-Ray Imagine: http://www.tooloop.com/wp-content/uploads/2013/12/Radius-Ulna-X-Ray.jpg
Whorls
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.
Plain
Whorl
Central
Pocket
Whorl
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
Delta
Delta
Double loop whorls are
made up of any two loops
combined into one print.
Accidental whorls contain two
or more patterns (not
including the plain arch), or
does not clearly fall under
any of the other categories.
Identify each fingerprint pattern.
Right Hand
Left Hand
Right Hand
Right Hand
Left Hand
Double Loop Whorl
Plain Whorl
Right Hand
Left Hand
Plain Arch
Tented Arch
Right Hand
Radial Loop
Right Hand
Left Hand
A Closer Look at Fingerprints
Image from ftp://sequoyah.nist.gov/pub/nist_internal_reports/ir_6534.pdf
T. Trimpe 2007 http://sciencespot.net/
1. Ridgeology: is the study of the uniqueness of friction ridge
structures and their use for personal identification.
2. 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 http://www.cs.usyd.edu.au/~irena/minutia.gif
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.
http://www.fdle.state.fl.us/CrimeLab/images/fingerrint%20comparison%20for%20afis.jpg
AFIS Video Link:
https://www.youtube.com/watch?v=ZKi1CKTRCQM
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
Crossover
Core
Bifurcation (fork)
Ridge ending
Scar
Island
Delta
Pore
http://cnx.org/content/m12574/latest/properties.jpg
How many ridge characteristics can you identify in this fingerprint?
http://www.dkfz.de/tbi/projects/bmcv/images/iu_it246_04s_fingerprint1.jpg
Let’s survey the class…
How do our fingerprint patterns compare to the expected averages?
Let’s determine their rate of occurrence…
Pattern
#
Total Prints
Arch
Loop
Whorl
How do our results compare to the averages?
60% - Loops 35% - Whorls 5 % - Arches
__% - Loops __% - Whorls __% - Arches
%
Forensic Science
T. Trimpe 2007 http://sciencespot.net/
How prints are
left behind:
- Ridges have small
pores along their
length
- oils and sweat
from pores leave a
copy of the ridge
marks
Type of prints found:
• Visible  ridges left in visible colour
(ex. from blood or paint)
• Plastic  impressions left in soft materials
(ex. wax, soap)
• Latent  invisible impressions left from
oils and sweat
1. Latent prints are impressions left by friction ridge skin on a
surface, such as a tool handle, glass, door, etc.
2. Prints may be collected by revealing them
with a dusting of black powder and then lifted
with a piece of clear tape.
3. Did you know? Camel hair is the most common animal hair
used to make fingerprint brushes. Now many brushes (like the
one above) are made out of fiberglass.
4. Some investigators use fluorescent powder and UV lights to
help them find latent prints on multi-colored or dark surfaces.
5. Magnetic powder can also be used to reveal latent prints. This
type of powder works better on shiny surfaces or plastic baggies
or containers.
6. The cyanoacrylate fuming
method (often called the
super glue method) is a
procedure that is used to
develop latent fingerprints on
a variety of objects.
7. During fuming the super glue heats up and attaches
to the amino acids in the fingerprint.
The evidence is placed in a super glue chamber to
develop the prints.
Click the icon to
view the Crime 360
Super Glue Video
8. Ninhydrin is a chemical that bonds with the
amino acids in fingerprints and will produce a blue
or purple color. It is used to lift prints from
surfaces such as paper and cardboard.
It’s time to make
some prints!
Avoid
Partial
Prints
GOOD PRINT
Get as much of the top part
of your finger as possible!
Directions to create Ink Prints
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
thumbprint.
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.
Try It on a balloon!
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: http://www.msichicago.org/fileadmin/Education/learninglabs/lab_downloads/fingerprint_analysis.pdf
Directions for lifting Latent Prints:
1 - Cover your table with white butcher paper or newspaper. You must dust
everything on the paper!
2 - Get a lifting kit from your teacher that contains black powder, brushes, and
clear tape.
3 - Press the pad of your right thumb on a CD or glass slide to make a print. Place
on the paper covering your table.
4 – Dip a brush lightly into the container of black powder and then tap off the
extra on the lid. You only need a very small amount of powder to dust the print.
5 – Hold the brush over the print and rotate it between your thumb and fingers.
Use the brush to remove any extra powder.
6 - Use a small piece of clear tape to lift the print and place it in the box on your
worksheet.
CAUTION: The black powder will be messy and isn’t easy to clean
up. Don’t dust anything without permission!
Clean Up
1 – Clean off the CDs or glass slides and put them back in the kit
with the brushes and tape.
2 – Have someone help you fold the paper in half and tap it to return
the extra black powder to the container.
3 – Put the black powder in the box and have it checked in by your
teacher.
4 – Get a towel and “dry” wash the table – especially the edges that
weren’t covered with paper.
5 – Get a wet towel to wash off the table and then wipe it with some
dry towels. Keep cleaning until all the black powder is off the table!