SCI 114
–
Scientific Principles of Forensic Science
Page 1
Laboratory Exercise: Fingerprint Analysis
Name: ______________________________
Date:___________________
Section# ________
Introduction:
Fingerprints
No two individuals have identical fingerprints and this uniqueness allows fingerprints to
be used in all sorts of ways, including background checks, biometric security, mass disaster
identifications, and criminal investigations.
Fingerprint analysis has been used to identify
suspects and solve crimes for more than 100 years, and it remains an extremely valuable tool for
law enforcement and forensic science. One of the most important uses for fingerprints is to help
investigators link one crime scene to another involving the same person. In addition, fingerprint
identification helps investigators to track a criminal’s record
(previous arrests and convictions).
i,ii
All fingers, palms, toes, and feet are covered in raised portions of the skin, arranged in
connected units called
friction ridges
.
When these ridges contact a surface, they leave a mark, or
an impression called a
fingerprint
.
iii
A fingerprint usually appears as a series of dark lines that
represent the high, raised portion of the friction ridge skin known as
ridges
, while the valleys
between these ridges appear as white spaces and are the low, shallow portion of the friction
ridge skin known as
furrows
.
iv,v
The imprint of a fingerprint consists of natural secretions
(composed of mainly water, oils, and salts) of the sweat glands that are present in the friction
ridge of the skin. Anytime an object is touched, traces of these substances are left behind in the
unique pattern of
an individual’s
friction ridges.
3
Fingerprints are grouped into three general
patterns
—
arches, loops,
and
whorls
—
depending on the shape of the ridges:
Arches
have ridges that enter from one
side of the fingerprint, rise in the center of the
fingerprint, and exit the opposite side from which
it entered; this resembles a wave-like pattern.
Tented arches
rise to a sharper point than
plain
arches
. Arches make up about five percent of all
pattern types
3
(
see Figure 1
6
).
Loops
enter from one side of the fingerprint, recurve,
and exit the same side from which they entered.
Loops can be subdivided into two categories; ulnar
loops and radial loops.
Their designation is based
upon if the loop opens toward the little finger or
towards the thumb.
If the opening is towards the
little finger, it is known as an ulnar loop.
If the
opening is towards the thumb, it is known as a radial
loop.
Loops account for approximately 60 percent of all pattern types
3
(
see Figure 2
6
).
Figure 2:
Loop Patterns.
Figure 1:
Arch Patterns.
SCI 114
–
Scientific Principles of Forensic Science
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- Fall '19
