Lesson 2
Fingerprint
Pre-Lesson Reading
1.
Fingerprint Principles:
According to criminal investigators, the use of fingerprint follows 3 fundamental
principles:
a.
A fingerprint is an individual characteristics because no two fingers have
yet been found to possess identical ridge characteristics.
b.
A fingerprint remains unchanged during an individual’s lifetime.
c.
Fingerprints have general ridge patterns that permit them to be
systematically classified.
2.
Origin of fingerprint:
a.
Take a look at your fingertip. You’ll see small ridges made of skin. The ridges have a
purpose. They help you get a better grip on stuff you pick up.
b. The ridges develop in the womb and remain the same throughout life, barring some
sort of scarring or trauma to the deep skin layer. Although people grow and increase
in size, the ridges became permanent and fixed in their patterns from about 17 weeks
of embryonic development, ridge patterns do not change like other parts of our
bodies.
c.
When the finger touches a surface, perspiration and oils are transferred onto that
surface, leaving a pattern called fingerprints.
3.
All fingerprints are classified into three categories on the basis of their general patterns:
a.
Arches
 Ridges enter on one side and exit on the other side.
 Approximately 6% of people exhibit this pattern
b.


Loops
Ridges enter on one side and exit on the SAME side.
Approximately 60% of people exhibit this pattern
c.


Whorls
Consists of circles, spirals.
Approximately 34% of people exhibit this pattern
4.
Types of fingerprint evidence:
a. Patent prints
These are clearly visible. They’re made when you touch something like paint or blood
and then touch other surfaces.
b. Latent prints
They’re formed when you touch something and the oil and sweat on your hand leaves
a print. Latent prints are mostly invisible to the naked eye. Fingerprinting dust makes
them visible.
c. Physical prints
These are made when you touch something like gum that leaves a clear impression of
your prints.
5.
Three common methods of latent print enhancement:
a.
Lifting powder Application

Work bests upon smooth solid surface, e.g. walls, glass, knife.

Fingerprint powders are colored, fluorescent, or magnetic materials that are very
finely ground and are brushed lightly over a suspected print to produce contrast to
the background. These powders typically are available in black, white and other
colors, including metallic.

Once the lifting powder has been successfully applied a fingerprint is then “lifted”
using a wide piece of clear smooth tape.
b.
Iodine Fumigation

Work bests upon light-colored light weight/low density objects, e.g. paper, fabrics

A small amount of iodine is placed at the bottom of a glass chamber. The object
bearing the suspected latent prints is then suspended from the top of the chamber.
The chamber is then sealed and chemical reaction occurs. The latent fingerprints
become dark brown in colour and photograph of the fingerprint will be taken.
WARNING: Iodine is irritating to skin and eyes. Do not breathe in iodine vapours.
c.



Cryanoacrylate Fumigation
Cryanoacrylate is a very strong glue. It has tendency to stick to the body oil
residue found in fingerprints.
Work bests upon dark-colored dense objects, e.g. guns, knife handles.
When Cryanoacrylate begins to react with the body oil residue in a fingerprint, it
leaves behind a whitish-grey film which is visible to the human eye. Photograph
of the fingerprint will be taken.
Lesson 2
Fingerprints
Worksheet 2.1
1.
Classify each of the following prints as loop, whorl or arch.
a.
2.
Fingerprint Basics
b.
c.
While searching a murder scene, you believe the following items may contain latent
fingerprints. Indicate whether prints on each item should be developed using fingerprint
powder or chemicals.
a.
b.
c.
d.
A leather sofa
A mirror
A painted wooden knife handle
Blood-soaked newspapers
3.
Fingerprints that deposited on a surface when oils and sweat are excreted from pores on the
friction ridges are called ________________ fingerprints.
4.
The most common fingerprint pattern is the _________________ .
5.
True or False
a. The individuality of a fingerprint is determined by its pattern.
b. Fingerprints cannot be changed during a person’s lifetime.
c. Arches have type lines, deltas and cores.
d. Identical twins have the same fingerprints.
e. Computerised fingerprint search systems match prints by
comparing the positions of bifurcations (分岔) and ridge
endings.
f. A fingerprint left by a person with soiled or stained fingertips is
called a latent print.
Lesson 2
Fingerprints
Worksheet 2.2
Practice the identification skills
e.g. fork
Figure 1
______________________________
Instruction:
1. Examine the fingerprint (Figure 1) with a magnifying glass if necessary.
2. To which class does the fingerprint pattern belong? Write down your answer.
3. Use Table 1 to help identify fingerprint ridgeline details. Locate and label at least 8
positions of ridgeline details in Figure 1.
Table 1 Fingerprint ridge details
Fork
Double Fork
Triple Fork
Delta
Dot
Bridge
Hook
Eye
Short Ridge
Ending Ridge