Transcript Chapter 4 Fingerprints

Chapter 4
Fingerprints
“Fingerprints cannot lie, but liars can make fingerprints.” - Unknown
Objectives

Learning Targets:
1) Define the 3 basic properties that allow
identification by fingerprints.
2) Recognize the general ridge patterns and
apply them to the primary Henry – FBI
classification.
At the Crime Scene
1) What is a fingerprint?
Fingerprint – impression of the pattern of ridges on the
last joint of a person’s finger.
At the Crime Scene
2) What are the properties of a fingerprint?
– Unique ridges.
– Consistent over an individual’s lifetime.
– Systematic classification used for fingerprints.
Classification of Fingerprints
3) How are fingerprints classified?
- 3 basic patterns
a) loops
b) whorls
c) arches
Classification of Fingerprints
4) What are loops?
 Loops – The loop pattern has one or
more ridges entering from one side,
curving, then going out from the same
side it entered.

All loops have a:
– Delta – a triangular area usually shaped like
the silt formation near the mouth of a river
flowing into the sea.
– Core – Near the center of the pattern.
Classification of Fingerprints
5) What are whorls?
Whorls – ALL whorls must
have at least 2 deltas and a
core
 4 whorl groups:

–
–
–
–
Plain Whorl
Central Pocket
Double
Accidental
Classification of Fingerprints
6) What are arches?
Arches – friction ridges enter
from 1 side of the finger and
exit the other side while
rising upward in the middle
 Arches do not have a delta or
core.
 2 types

– Plain Arches
– Tented Arches
Classification of Fingerprints
7) What is FBI method of classification?
Henry – FBI classification – allows all 10 fingerprint
types in the world to be divided into common
groups.
- IMPORTANT: When prints are sent to the FBI, the
Henry-FBI classification system allows for the
elimination of millions of prints SO that they only
have to hand compare a dozen prints.
Ridge Classification
8) What are minutiae?

Minutiae – fine structure of ridge characteristics
pg 57 in your book for different types
Presenting Fingerprints as Evidence
9) How are fingerprints used in court?
No legal requirements in US on # of
points that match
 Criminal courts usually accept 8-12 points
 Challenge: 150-200 minutiae in a properly
rolled fingerprint, the problem is getting a
good, readable print to work with.

Presenting Fingerprints as Evidence
10) What can affect fingerprints?

Certain professions can affect a fingerprint
– Ex. Concrete workers fingerprints become indistinct
over time because alkalinity of cement and gypsum
can dissolve proteins.

John Dillinger (Public Enemy # 1 in 1930) – paid
a doctor $5000to dissolve his fingerprints &
perform facial surgery
Types of Prints
11) What are the 3 types of prints?
Plastic prints – indented/molded prints – press a
finger into a plastic-like material (i.e. paint,
putty, soap)
 Visible prints – left by a finger that has touched,
colored material such as blood, paint, ink, etc.
 Latent prints – essentially invisible & must be
developed by chemical/physical means – left by
deposits of body oils & perspiration

Visualizing Latent Prints
12) How are prints developed?
Dusting – dusting print with a fine powder
 Chemical methods – chemicals (i.e. iodine,
ninhydrin) generally effective for soft,
porous surfaces as paper

The History of Fingerprints
13) When did dactyloscopy begin?
Dactyloscopy – study of fingerprints
 Started in 19th century in India with
William Herschel

Other Methods
14) What computer program does the FBI
use to identify fingerprints?

Automated Fingerprint Identification
Systems (AFIS)