Fingerprinting (latent)

Biotechnology II

Skin Layers

Epidermis: superficial layers of keratinized stratified squamous epithelium

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