FORS-2107EL Lecture Notes - Lecture 5: Ulnar Nerve, Ninhydrin, Sebaceous Gland
27 Jun 2018
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Forensic Science - Day 5 2018.01.22.
Fingerprints I
Definition of Friction Ridge Patterns
-They are the pattern of ridges that appear on our fingers, feet, hands are meant to
help friction
-This is another name for “fingerprints”
-In vitro, therefore in the uterus, they begin as primary friction ridges within the dermal
layer, and sweat glands will form within this layer and proliferate from the primary
ridges
-After 15 weeks of gestation, primary ridges stop forming and secondary ridges begin
to form
-The layer between the dermis and epidermis is where the template for the surface
ridges we see
Forensic Principles of Fingerprint Analysis
-Fingerprints are used in forensics as a form of associative evidence, to link a person
to an object or place
-Presumption that are made:
-Fingerprints have to be (unique) characteristics to an individual
-Fingerprints remain unchanged over time (barring external influence, such as injury
or mutilation)
-Fingerprints have general ridge patterns that may be systematically classified
Types of Friction Ridge Patterns
-Prints may be of various types:
-Patent prints: those are ones that can be seen (essentially) with the naked eye, ex.
prints on glass), which come from dirt on fingers, or bloody prints
-Latent prints: those which need external treatment to make the print visible, which are
composed of sweat and body oils left behind
-Plastic prints: impressions left in a malleable material, like silly putty, waxy putty, (ex.
used to form window seals)
Minutiae of Friction Ridge Patterns
-Minutiae are ridge characteristics that are examined and comprised together in
assessment and comparison of fingerprints
-All put together, they can make up different kind of shapes and patterns
find more resources at oneclass.com
find more resources at oneclass.com
Classification of Friction Ridge Patterns
-Classified in 3 primary categories:
-Loops
-Has atleast one ridge which enters on one side of the print and then curves back
towards, and exits on the same side
-Ulnar loops: those which begin on the same side of the hand as
the little finger (begin/end towards the little finger)
-Radial loops: those which begin on the same side of the hand as
the thumb (begin/end towards the thumb)
-Are surrounded by two diverging ridges (points) and the point of
divergence is called a delta
-Arches
-These are patterns that have a rise and fall pattern, and
are the rarest of the three pattern types, the ridges will
enter on one side of the finger and exit on the other, with
the raised portion in-between
-Plain arches: have a rounded peak
-Tented arches: have sharp peaks
-Whorls
-Wholes are sub-classified into: plain whorls,
central pocket loop, double lood, and
accidental
-Central pocket loops and plain whorls have at
least one continuous loop which may be
closed (circular) or spiral
-To tell a central pocket loop to a plain whorl
they draw a connecting line between two deltas, if the line touches the circular
core, the whorl is categorized as a plan whorl, otherwise it is a central pocket
loop
-Double loops have two loops that swirl around each other
Classification of Friction Ridge Patterns
-Print classification in the US is base on
the FBI system, which is a modification
of the original Henry System which is a
series of fractions based on the 10
fingers
-It takes all 10 fingers, and creates a ratio
based on all them
-They take each finger and check if there
is a whorl or not and use this chart to
make the fractions, 1 is the first fraction, 2
is the second fraction, 3 is the third
fraction, and so on
find more resources at oneclass.com
find more resources at oneclass.com
