Fingerprints
Background Information
 Each
fingerprint is made up of friction
ridges, that do not change over time
(unless scarring occurs)
 Fingerprints are formed in the womb
 Each fingerprint is a deposit of wastes
when a person comes in contact with a
surface
 98 % is water & salts, 1% oils, 1%
amino acids
Prints at a Crime Scene
Divided
into 3 types
Patent Print
Plastic Print
Latent Print
Patent Print
Can
be seen with the naked
eye
Made by a hand that had
blood, grease, oil, or any
other sticky substance on it
Plastic Print
Visible
to the naked eye
Formed when an
impression is made in a soft
substance such as putty,
glue, dust, or butter
Latent Print
Most
common type
Cannot be seen without
applying powder or chemicals
Substances adhere to the
amino acids or oils in the
fingerprint and make it visible
Patterns of Fingerprints
3
basic types of patterns
Arch : 5% of population
Loop : 65% of population
Whorl : 30% of population
Basic Fingerprints
ARCH
LOOP
WHORL
Plain Arch
Left Radial
Loop
Left Ulnar Loop
Plain Whorl
Tented Arch
Right Radial
Loop
Right Ulnar
Loop
Central Loop
Whorl
Double Loop
Whorl
Accidental
Whorl
The Arch
Formed
when the ridge lines
go from one side, rises in the
middle, and leaves on the
other side (like a wave)
Tented arches are more
pointed
No ridgecount
Example of Arch
The Loop
 Ridge
lines enters & exits on the
same side of the finger
 Type is determined by the direction
the ridges come & leaves
 If it is from the thumb-side of the
finger, it is called a RADIAL LOOP
 If it is from the little finger side it
is called an ULNAR LOOP
Examples of Loops
The Delta
Whorls
are subdivided using a
ridge characteristic called a
DELTA
DELTA: Triangle pattern
(ridge forks & nearby ridge)
Whorls have 2 deltas, loops
have 1 delta & arches have 0
deltas
The Whorl
Ridge Characteristics
BIFURCATION
(or fork):
ridge splits into 2 friction
ridges
ENCLOSURE: forms an oval
ENDING RIDGES: ridges
that stop abruptly
Ridge Characteristics
Continued
SHORT
RIDGES: begin & end
abruptly, traveling a short
distance
RIDGE DOT: isolated ridge
that’s length is approximately
its width
Examples of Ridge Characteristics
Identifying Fingerprints
 8-12
points of comparison must be in
common to declare the 2 prints a match
 When a partial print is available, as
many characteristics must be matched
as possible
 Characteristics can be matched to the
AFIS (Automated Fingerprint
Identification System)
Example of Positive ID
Dusting for FIngerprints
NONPOROUS
SURFACES
WOOD
METAL
PLASTIC
GLASS
TILE
Chemically Fingerprinting
Cyanoacrylate (Superglue), Iodine, Ninhydrin
POROUS SURFACES
PAPER
UNFINISHED WOOD
WALLPAPER