Layers
Dermis: deeper than epidermis; sheet of irregular fibrous dense connective tissueResponsible for most of the structural
strengthBlood vessels supply dermis and epidermisContains sensory nerve endings which are
responsible for sensations such as hot and cold
Layers: Dermis continued
Papillary layer: bumpy superficial portion of dermis attached to the epidermis.Papillae form regular rows in thick skin but
are irregularly arranged in thin skin. This is why fingerprints and the soles of your feet have distinct ridges. These ridges also help with our ability to grip things.
Structure of Skin
Did you know… stretch marks develop from a rupture in the dermis and the epidermis is noteffected.
Hair
Did you know…Hair is present on all skin surfaces except
the palms, soles, lips, etc.
Hair follicle extends from surface into the dermis and contains a hair root
Hair shaft protrudes above the surface of the skin
Fingerprints
HistoryJapanese used thumb print as a signature
on documents until 1860.First used in crime in 1901 by Sir Edward
Richard Henry3 Patterns
WhorlLoopArch
Fingerprints
Most natural finger prints consists of secretions of the skin’s glands
3 GlandsEccrine: secretes H20 and inorganic &
organic contaminantsSebaceous: secretes fatty acids and
hydrocarbonsApocrine: secrete cytoplasm and nuclear
materials such as carbohydrates
Fingerprints: Interesting Facts
Fingerprints are completely formed before birth Genes determine finger prints but there can be slight
differences between identical twins due to slight movement during development.
Yes, you can burn them off with acid BUT they will reform in exactly the same pattern you were born with
Ridge pattern never changes even as you get older.
Latent fingerprints
Fingerprints left behind at a crime sceneMay or may not be visible
Visible usually have blood, grease, dirt, etc. in them to display the background
Non visible need treatment “latent print development” to be seen
Methods of Detection
Types of printsLatent printVisible print – deposited ink, blood, dirtPlastic print – impression in a soft surface
Locating prints – RUVIS
Categories of Fingerprints
Loop – ridge lines enter one side of pattern and curve around to exit from the same side of pattern. (65%)Ulnar loop – opens toward little fingerRadial loop – opens toward thumb
Ulnar Loop Radial Loop
Categories of Fingerprints
Whorl – ridge lines rounded or circular and have two deltas(30-35%)Plain whorl
Central pocket loop
Double loop
Accidental loop
Categories of Fingerprints
Arch – ridge lines enter print from one side and exit from the other (5%)Plain
Tented
Developing PrintsPowders
CharcoalMagneticFluorescent
Chemicals Iodine fuming (sublimation) NinhydrinPhysical developer (silver nitrate) Super Glue fuming Alternate Light Sources/ LED
Preservation of Developed Prints
PhotographsPrint surface should be removed in its
entirety (covered with cellophane)Lifted from surface with tapeDigital imaging into pixels – allows
adjustments to be made to enhance picture
Classification of Fingerprints
Henry system – numerical system involving the presence or absence of the whorl pattern on each finger as part of the primary classification.. This does not identify someone, only reduce the
number of possible candidates
AFIS – 10 print system that can search 500,000 stored ten-prints in 0.8 seconds Data entered now by Livescan rather than ink rolling. Human decisions must still be made Software incompatibilities among states
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