IV.+Fingerprints

__ **Fingerprint Analysis** __ __**The Skin**__
 * Fingerprints are unique to every person and never change.
 * No one has identical fingerprints, not even identical twins.
 * Fingerprints are a reproduction of friction skin ridges found on the palm of the hand on the fingers and thumb.
 * They are compared on the basis of friction ridge formation, which are formed during the third and fourth months of fetal development.
 * There are many characteristics of ridges in which fingerprints are analyzed by such as: ridge endings, bifurcations, enclosures, and the ridge island (which is also known as the ridge dot).
 * Usually 8 to 16 ridge comparisons are needed in order to distinguish if two fingerprints are in fact the same.
 * Our skin is composed of many layers of cells.
 * // The Epidermis // - outermost layer of the skin
 * // The Dermis // - inner layer of the skin
 * // Dermal Papillae // - layer of cells that separates the epidermis from the dermis and is responsible for the form and pattern of ridges that are on the surface of the skin
 * Each ridge contains pores which are connected to sweat glands underneath the skin and when anything comes into contact with our fingers, fingerprints are left on the surface (which are the finger’s ridge patterns).
 * There are two types of fingerprints, ones which are invisible to the naked eye and others that are visible
 * Latent fingerprints are those that are invisible and occur when the perspiration on the fingers comes in contact with the surface and leaves an impression.
 * Latent fingerprints can be left on practically any surface such as a desk, mirror, or drinking glass.
 * Visible fingerprints are those fingerprints, which are visible to the naked eye on a surface after they have been in contacted with colour materials such as paint, ink or blood.

__**Fingerprint Classification:**__ Fingerprints are divided into three patterns: 1. **Loops** - this pattern is characterized by ridge lines that enter from one side of the pattern and curves around to exit from the same side of the pattern
 * if the loop opens towards the little finger it is called a //ulnar loop//
 * if the loop opens towards the thumb it is called a //radial loop//

2. **Whorls** - ridge patterns which are generally rounded and circular with two deltas - whorls are divided into four patterns A) plain whorl and central loop pocket - include one ridge that makes a complete circuit which can be in any form. B) double loop - two loops combined in a fingerprint C) accidental - two or more patterns (excluding the plain arch) or a pattern which cannot fit into any of the other categories

3. **Arches** - ridge lines enter the fingerprint from one side and flow out from the other side A) plain arches - most simplest, enter on one side and flow out on the other side B) tented arches - similar to the plain arches but rise sharply at the center at an angle which is less than 90 degrees
 * usually the least common and do not have type lines, deltas or cores
 * two distinct type of arches:
 * usually have an arch in the center of the pattern, like a wave
 * The **delta** is ridge point which is found in front of the point of divergence or outside of the central pattern.
 * The **core** is the center of the pattern on a fingerprint.

**__ Forensics: __** Many crime scene fingerprints are what are called latent prints. Latent prints are a fingerprint made by the deposit of oils and/or perspiration; which is invisible to the naked eye. There are many ways to detect latent prints. The first is the use of fingerprint powders. Particles of powder adhere to residue left by the friction ridge on the skin of the finger. Latent prints deposited on hard and non-absorbent surfaces (e.g., glass, mirror, tile, and painted wood) are preferably developed by the application of a powder. The colour of the powder used is dependant on the surface for which the print may be on. Best colour to use should contrast with surface being dusted. **Grey dust**, made of aluminum powders, is used on dark-coloured surfaces. While, **black powders** that are made from charcoal are useful on light-coloured surfaces. **Fluorescent powders** are seen under ultraviolet light. This type of powder allows investigators to avoid having the colour of surface obscure print.

The second way to detect latent prints is by the use of chemical enhancement:

** Iodine fuming **. It is the heating of iodine crystals that create vapors, which combine with latent prints to make them visible. The suspected material is then placed in an enclosed cabinet with the iodine crystals, which is a process called **sublimation**.

** Cyanacrylate ** or **Super Glue® Fuming** is the technique for visualizing latent prints on nonporous surfaces, such as electrical tape, plastic bags, or metal. Cyanoacrylate fumes from the glue adhere to the print, usually producing a white latent print. Placing the glue on absorbent cotton treated with sodium hydroxide or heating glue creates the fumes. The suspect material and fumes are then contained within enclosed chamber for several hours.

** Chemically induced fluorescence: ** Fingerprints are treated with chemicals that would induce fluorescence when exposed to lasers, or high-intensity light sources, such as quartz halogen, xenon arc, or indium arc light sources. Following the identification of a latent print**,** a photograph must be taken before any further attempts at preservation are made. Prints that are found on small object are preserved in their entirety. “Lifting” with a broad adhesive tape best preserves prints on large immovable objects**,** then the tape is placed on a properly labeled card that provides a good background contrast with the powder.