Unit 2: Fingerprints

Pore

A white dot - this is a sweat pore

Enclosure

Also called a lake - Where the ridges split to create a "hole"

The Ninhydrin test: When to use it

Best to use on paper - It can be used to develop very old prints (made over 30 years ago!). - The prints developed will be PURPLE in color and are permanent. (should not fade)

Accidental Whorl

3 deltas - Doesn't clearly fit under any category

An Island

A "dot" on the fingerprint, which is a very short ridge

Minutiae

Distinguishing features of the finger print - Bifurcations and ridge endings account for the vast majority of all minutiae that are used to compare prints! 1) Always the FIRST minutiae that are compared and matched up

Dactylogram

A complete set of inked fingerprints (10 digits)

Bifurcation

A fork where two or more ridges split - Double bifurcation: multiple ridges split

Delta

A triangular-shaped pattern where 3 different fingerprint ridges meet. - A loop has at least one delta - Whorls have two deltas

Double Loop Whorl

Two Loops and Two Deltas - An S shape

Plain Whorls

Two deltas and at least one ridge making a complete circuit - If you draw a line between the two ridges, it will cut one ridge line will but the complete circuit

General Classes of Fingerprints

Loops 65%, Whorls 30%, Arches 5%, Accidental whorls <1%

Visualization

Making latent prints (or partial prints) visible

The Ninhydrin test: Potential Problems

Ninhydrin causes most inks to run! - So for example it should never be used on a hand written ransom note until you have photographed it

The Ninhydrin test

Ninhydrin is a liquid chemical that turns latent prints a purple-blue color. - The Ninhydrin reacts with traces of proteins (amino acids) in human perspiration

Silver Nitrate: When to use it

On paper

Iodine Fuming

Solid Iodine sublimates (turns directly from a solid into a gas) when gently warmed. - The iodine vapor reacts with oils from the print. - Note however that oil is one of the first compounds to break down and be lost from a latent print.

Tented Arch

The Arch is higher and some of the high ridges start and end inside the arch - they do not travel right across (from one side to the other)

Mayfield Madrid Mistake

11 March 2004 - Madrid Train Bombing - Killed 192 people and injured 2,000 - Spanish investigators found an abandoned set of detonator caps inside a plastic bag that bore a single, incomplete fingerprint. - Arrested Oregon lawyer Brandon Mayfield, stating his print was a match - Two and a half weeks later, a chagrined FBI was forced to release Mayfield after Spanish police arrested an Algerian national — one of several terrorists later charged with the crime — and found one of his fingerprints to be a much better match. 1) Sued the government for a violation of civil rights 2) Bias, as he was muslim? - Couldn't find exact match, so it found close matches, in this case, one of the close matches was Brandon Mayfield - Parts of a fingerprint, Minutiaes, can be so similar that two people can be identified to one latent print

Whorl

All Whorls have at least two Deltas - There are Plain Whorls and Central Pocket Whorls

Inked Prints

An individuals inked prints - A full set of inked finger prints typically contain rolled (10) and flat prints.

4 different categories of prints

Inked Prints, Patent Prints, Latent Prints, Plastic Prints

Central Pocket Whorls

Inner circular pattern not cut by line - No inner pattern (circle) ridges are cut by a line joining the two Deltas

IAFIS

Integrated Automated Fingerprint Identification System - Digital scanners can capture an image of the fingerprint. - computer image can be used to map distinguishing features called Minutiae on the fingerprints. It can then search the IAFIS data base for prints with matching minutiae points. - After the computer has established a match, THEN a human agent trained in fingerprinting evaluation MUST HAND CHECK the actual print that is on file with the evidence print - IF there are at least 12 pts of minutiae that match up, then the two prints are a match

Iodine Fuming: When to use it

Iodine fuming can be used to develop fingerprints on fabrics and rough surfaces. - Because prints developed by this method disappear rapidly no drastic changes are made to the paper or any writing on the paper (Unlike the Ninhydrin test!)

Crossover

Lines that criss cross on the fingerprint

Arches

No deltas or cores present - Two types: Plain Arch and tented arch - Arch ridges enter on one side of print and exit on the other

Iodine Fuming: Potential Problems

Once the iodine print is removed from the container, the print will begin to fade - so it must be photographed straight away. - Even if it is sprayed with starch - which will produce a semi-permanent print - it will eventually fade (it is not permanent)

Fingerprints

Raised "Skin ridges" that allow you to grip objects. - Found on the tips of your fingers and toes. - The koala is one of the few mammals (other than primates) that has fingerprints! - Everyone's fingerprints are unique to them; no two individuals have exactly the same fingerprints (Even identical twins!) - An individual's fingerprints remain unchanged throughout life (unless deep scars are obtained at some time and then scars will be evident among the fingerprint ridges) - Fingerprints can be classified and can be used as a source of identification and physical evidence.

Loop

Right and left loops - Right loop is also called an Ulna loop - A Left loop is also called a Radial loop - Loops must have one delta and one or more ridges that enter and leave on the same side. -

Scars or wrinkles

Seen as white lines on a fingerprint - The technical name for this white line is a Cicatrix

Silver Nitrate: Potential Problems

Silver nitrate development is destructive so if it is to be used it must be used after all other methods have been attempted.

Silver Nitrate

Silver nitrate solution reacts with the salt in perspiration

The Ninhydrin test: How it's done

Spray the paper thoroughly with the ninhydrin spray - Let dry completely - Prints begin to appear within 30 min, and can be developed faster if they are heated to a temperature of 80 degrees Celsius. - The prints developed will be PURPLE in color and are permanent

Superglue Fuming: Potential Problems

Superglue has to be the last method used since no other chemical substance will react with the fingerprint after it is coated with the superglue

Core

The Name given to the central part of a whorl or loop

Iodine Fuming: How it's done

The article is placed inside an enclosed space with iodine crystals then it is gently heated. - The iodine vapor given off by the crystals combines with traces of oil in a chemical reaction that leaves a visible pattern (yellow/brown) - It can then be sprayed with starch to turn it blue/black.

Plain Arch

The basic arch structure (aka simple arch)

Superglue Fuming: When to use it

The fumes can be applied by heating the object in a closed cabinet or by forming an entire closed space, such as the interior of an automobile - the fumes should reveal every latent print!

Superglue Fuming: How it is done

The object is put into a closed chamber. - Superglue is added and the fumes will interact with everything in the chamber. - After exposure to superglue (cyanoacrylate), the fingerprints can then be captured on film as is or treated with a special fluorescent dye that sticks to the fingerprint and is detected by UV light.

Order of Chemical Testing

The order in which the techniques are used is important. - The following order should be used to develop fingerprints: Iodine fuming, ninhydrin, silver nitrate OR superglue fuming - Iodine fuming is not permanent (adding starch will only make it semi perm - 3 or 4 weeks only then it fades) - If Ninhydrin fails, silver nitrate can be used. (but superglue will not then be a further option - because the Silver nitrate test will wash away all the fatty oils and proteins from the surface) - Superglue fuming, if used, should also be used last - because the Ninhydrin and iodine test will not be able to work on the hardened glue prints

Silver Nitrate: How it's done

The print is sprayed lightly with silver nitrate and allowed to develop - It is made visible under ultraviolet light - The print will appear as a reddish-brown color - when placed under ultraviolet

Latent Prints

These are invisible prints- they must be visualized (this means made visible - methods of visualization include: dusting/iodine/super glue) - the most common type of prints found at a crime scene. - Latent fingerprints are made when the natural oils and perspiration that exist between the fingertip ridges are transferred to a surface by touch. - Latent prints are invisible, they are much harder to detect and preserve (lift) than Patent or Plastic prints. - Fingerprint samples can easily be ruined if an incorrect chemical method is used to "develop them" (make them visible) - Often times, fingerprints are the only evidence prosecutors may have to convict a criminal. Therefore, it is vital that the print is handled with care and preserved properly. - ONLY about 10% of ALL the Latent fingerprints that are visualized from a crime scene (using traditional powder or chemicals) are of sufficient quality to be used in a court of law.

Patent Prints

These are visible 2D prints- (example: blood)

Plastic Prints

These are visible 3 D prints- These leave an indention in/on a soft object (example: in bubble gum/bar of soft soap/clay/mud)

Superglue Fuming

When super glue releases fumes they interact with the proteins (amino acids) that are found in the fingerprint residues

Bridge

When two bifurcations are linked together

Can You Erase Your Fingerprints?

Yes - You would probably still have a distinctive scar/pattern showing where they had been removed