the science of fingerprint identification. it has served all governments worldwide during the past...

The Science of Fingerprint Identification

The Science of Fingerprint Identification

• It has served all governments worldwide during the past 100 years to provide accurate identification of criminals.

• No two fingerprints have ever been found alike in many billions of human and automated computer comparisons.

Fingerprint Facts

• Fingerprint identification remains the most commonly used forensic evidence worldwide

• It outperforms DNA and all other human identification systems to identify more murderers, rapists and other serious offenders (fingerprints solve ten times more unknown suspect cases than DNA in most jurisdictions).

The Integumentary System• The skin is the body’s largest organ

• Skin is composed of 3 layers– Epidermis– Dermis– Subcutaneous layer

• Dermal papillae are extensions of the dermis into the epidermis and increase the surface area of these two layers

• Take a look at the dermal papillae and corresponding epidermal ridges in the figure . The dermis and epidermis fit together like stacked egg-carton bottoms.

What is a Fingerprint?• The creation of minute ridges and valleys

(also called friction ridges) found on the hand of every person due to the phenomenon of dermal papillae.

• In the fingers and thumbs, thesefriction ridges form 3 major patterns/types– loops, whorls and arches

• When oil from the body mixes with sweat and dirt and you touch something, these adhere to the surface of the object, leaving a print.

Friction Ridges

• The skin over most of the body is relatively smooth. 'Friction Ridges', however, are found on the digits, palms and soles. They are called 'friction' ridges because of their biological function to assist in our ability to grasp and hold onto objects.

Reasons Why Fingerprints Are Used for Identification Purposes

• 1) Ridge patterns and the details in small areas of friction ridges are unique and never repeated

• 2) Friction ridges develop on the fetus in their definitive form before birth.

• 3) Ridges are persistent throughout life except for permanent scarring.

• 4) Friction ridge patterns vary within limits which allow for classification.

Fingerprint Classification

• Fingerprint classification assists to narrow the search but is not part of the actual identification process. Its importance is clear though if you consider the huge task you would be faced with if, after taking thousands and thousands of fingerprints, you had no method to file and retrieve them.

• Remember the 3 types?

Identical twins have the same DNA

configuration but they do not have identical

friction ridge configuration.

Fingerprint Pattern Types

• Loop

• Whorl

• Arch

The Loop

The Whorl

The Arch

Each of the three pattern types have focal points which

are used for classification.

• Most fingerprints have a shape where there is a center visible. That center is called "the core", (see top). Another place is the place where a lot of lines come together "the delta", (see bottom).

The Loop

• In the Loop pattern there are two focal points: the Core, or the center of the loop, and the delta. The Delta is the area of the pattern where there is a triangulation or a dividing of the ridges. When recording fingerprints, the delta and the area between the delta and the core must be completely recorded.

The Whorl

• A Whorl pattern will have two or more deltas. For a whorl pattern, all deltas and the areas between them must be recorded.

The Arch

• The Arch pattern has no delta or core; but, it too, must be fully recorded so that its individual characteristics can be readily distinguished.

Fingerprint Patterns(Based on the Henry Classification System)

• The Arch

• The Tented Arch

• The Loop (Ulnar or Radial)

• The Whorl

• The Twinned Loop

• The Central Pocket Loop

• The Lateral Pocket Loop

• The Composite

• The Accidental

The Arch

• The Arch pattern is made up of ridges lying one above the other in a general arching formation

The Tented Arch

• The tented arch pattern consists of at least one upthrusting ridge, which tends to bisect superior ridges at right angles, more or less

The Loop (Ulnar or Radial)• The loop pattern consists of one or more free

recurving ridges and one delta.

• In order to distinguish between ulnar and radial loops you must:

• 1) know from which hand the loop pattern comes from and;

• 2) place your hand palm side down over top of the impression and determine if the recurving ridges originate from the little finger side or the thumb side.

• If the ridges flow in from the little finger side this would be an 'ulnar' loop. If the ridges flow in from the thumb side this would be a 'radial' loop.

The Loop (Ulnar or Radial)

The Whorl• The whorl pattern consists of one or more

free recurving ridges and two points of delta. When the line of the fingerprint disc is placed on the two points of delta, it will bisect at least one of the ridges belonging to the core group.

“The Happy”From Mrs. Witherington’s

Classification System

The Twinned Loop

• In the twinned loop pattern, the recurving ridges present two loop formations, separate and apart. There are two points of delta. The flows for the deltas originate from the same side of the pattern.

The Central Pocket Loop• The central pocket loop pattern consists of

one or more free recurving ridges and two points of delta. When the line of the fingerprint disc is placed on the two points of delta, it will fail to bisect any of the ridges belonging to the core group.

The Lateral Pocket Loop• In the lateral pocket loop pattern, the

recurving ridges present two loop formations, separate and apart. There are two points of delta. The flows for the deltas originate from the same side of the pattern.

The Composite• The composite pattern is composed of two

or more different patterns, separate and apart exclusive of the arch.

The Accidental• Fingerprints in this category contain two or more

distinct types of patterns with the exception of the plain arch, with two or more deltas, or a pattern that has some of the requirements for two or more different types, or a pattern that conforms to none of the definitions.

Fingerprint Up-close

Fingerprint Minutiae

Fingerprint Minutiae (Details)

• ridge endings - a ridge that ends abruptly • ridge bifurcation - a single ridge that divides into two

ridges • short ridges, island or independent ridge - a ridge that

commences, travels a short distance and then ends • ridge enclosures - a single ridge that bifurcates and

reunites shortly afterward to continue as a single ridge • spur - a bifurcation with a short ridge branching off a

longer ridge • crossover or bridge - a short ridge that runs between two

parallel ridges

Why Are Fingerprints a 100% Reliable Means of Identification?

• Fingerprints never change

• No two fingerprints are identical

Integrated Automated Fingerprint Identification System or IAFIS

• IAFIS, is a national fingerprint and criminal history system maintained by the Federal Bureau of Investigation (FBI)

• Provides automated fingerprint search capabilities, latent searching capability, electronic image storage, and electronic exchange of fingerprints and responses, 24 hours a day, 365 days a year

http://www.fbi.gov/

IAFIS • IAFIS maintains the largest database in

the world, containing the fingerprints and corresponding criminal history information for more than 47 million subjects in the Criminal Master File

• Just a few years ago, a fingerprint check could often take three months to complete

• As a result of submitting fingerprints electronically, agencies receive electronic responses to criminal ten-print fingerprint submissions within two hours

IAFIS became operational in July 1999.

Fingerprint Identification

• Types of prints– Latent– Patent– Plastic

Latent Prints

• Any chance or accidental impression left by friction ridge skin on a surface, regardless of whether it is visible or invisible at the time of deposition

Patent Prints

• Friction ridge impressions of unknown origin which are obvious to the human eye and are caused by a transfer of foreign material on the finger, onto a surface. Because they are already visible they need no enhancement, and are photographed instead of being lifted

Plastic Prints

• Friction ridge impression from a finger or palm (or toe/foot) deposited in a material that retains the shape of the ridge detail.[4] Commonly encountered examples are melted candle wax, putty removed from the perimeter of window panes and thick grease deposits on car parts.

Fingerprint Development, Lifting and Documentation

• Locating visible or plastic prints at a crime scene is usually not a problem because the prints are visible to the eye.

• Latent prints are more difficult and require the use of powders or chemicals to make the prints visible. Not always found in the crime scene.

• The investigator is presented with numerous methods to make latent prints visible to the eye.– The method of choice will depend on the type of

surface that is being examined.


• Hard or non porous surfaces:– Glass, mirror, tile, painted wood, ect.

• Powders or Super glue fuming.

• Porous or soft surfaces:– Papers, cardboard, cloth, ect.

• Treatment with one or more chemicals.


• Fingerprint powders are commercially available in a variety of colors and compositions.– When applied to a non porous surface with a camels hair,

fiberglass, or feather duster brush the powder adheres to the perspiration and oils left on the surface when touched.

• Gray and black powders are usually adequate for development of latent fingerprints.

– Black for light colored surfaces.– Gray for darker colored surfaces.

• The application of powders should be done lightly. The use of too much powder will destroy the characteristics of the print (clog the ridges).

• If the brush is run over a print too hard or too much it can destroy the print (erase).


• Magnetic powders are available for development of latent prints.– Spread on the surface with a magnet in the

form of a magna brush.• Does not have any bristles to come into contact with

the surface so there is less chance of destroying the print.

– Especially useful on items such as finished leather and rough plastics where the surface tens to hold regular powders.

– Available in florescent colors to help bring a print to the surface and photograph it against backgrounds that would not allow good visibility with non florescent powders.


• Chemical Methods:– Iodine fuming

• Oldest of the chemical methods• A Solid Crystal that when heated is transformed to a vapor without passing

through a liquid phase– This is known as Sublimation

• Item to be processed can be placed in a fuming chamber which is the best way if possible.

• For items too large, such as a wall or door iodine fumet's work well. – Break the tube housing the crystals and blow through the tube

directing the vapor over the area you wish to process and the print will develop.

• Iodine prints are not permanent and will fade once processed.– Photograph the prints as soon as they are developed for best results.

• If print is sprayed with a 1% solution of starch the print will turn blue and remain for several weeks or months.

– No guarantee on how long the print will remain visible.


• Chemical Methods:– Ninhydrin:

• Ninhydrin reacts with the amino acids present in trace amounts in the perspiration left behind when a surface has been touched.

– Forms a deep purple color.

• Safety.– Refer to the MSDS sheet for safety protocol.

» Wear rubber gloves, and face shield.» Use with hooded ventilation, out door use is not adequate

protection from fumes.

• Application.– Sprayed.– Dipped.


• Chemical Methods:– Physical Developer.

• Reacts with lipids, fats, oils and waxes present in fingerprint residues.

• Used on porous objects.– Use as the last process in the chemical development

sequence.» Iodine, DFO, Ninhydrin, and Physical Developer.» Photograph each process as it is done and document the

resulting prints.» The next process could destroy the prints.

– Safety :» Non-porous gloves, eye protection.» Eye wash station or emergency shower nearby.


• Super glue fuming:– Super glue fuming was developed in Japan in

1978.– Gained wide acceptance in the U.S. in 1982.

• Used to develop prints on non-porous surfaces.– Metal, electrical tape, leather, plastics.

– Safety precautions:• See MSDS sheet for safety protocol.

– Do not inhale fumes.– Avoid contact with the skin.


• Super glue fuming:– Materials required.

• Chamber.– Prefabricated – sold ready to go.– Portable – sold and ready to transport to the scene.– Suitable container that will retain the fumes and allow the

processing to take place:» Plastic bags, cardboard boxes, paper bags, ect.

– Super glue.– Accelerator –(Heat source (optional)).

» Hot plate.» Hand held Wand.» Cotton balls.


• Super glue fuming:– Easy fuming.

• Place the item to be processed in suitable chamber.• Place the item to be processed in the chamber.• Place wad of cotton balls in the chamber, or a hot

plate.• Place the super glue on the cotton, or on a suitable

dish or piece of foil onto the hot plate.• Seal the container.• Let stand for approximately 10 minutes, check after

five minutes if using hot plate or wand .• Remove the item form the container check for prints.


• Super glue fuming:– Items affecting fuming times and results.

• Temperature.• Size of container in relation to size of evidence processed.• Amount of super glue used.

– When developed prints will appear white.– If over developed the print and the surrounding area

of the print will appear white.• This will make the background fluoresce along with the

print and the print will appear as a glowing blob when fluorescent powder or chemical is applied.

– The powder or chemical will adhere to the white residue.


• Small Particle Reagent (SPR).– Application.

• Spray - Shake the solution thoroughly.– Spray the item to be processed.– Shake bottle between sprays.– Spray the area with clean water and watch for separation of the water

from the area with the prints.» Will look similar to the reaction of water on a surface with a grease

spot.• Dip - Use a baking dish or photographic pan.

– Half gallon jar can be used for small items.– Shake the solution.– Pour into container.– Immerse item to be processed for two to three minutes.– May have to immerse twice.– Remove and gently rinse with clean water.


• Small Particle Reagent (SPR).– Prints will appear dark gray on light surfaces

and light gray on dark surfaces– Wait until developed prints are thoroughly dry

and photographed before lifting • Do not attempt to accelerate drying by the use of a

hair dryer

Happy Thanksgiving!!

the science of fingerprint identification. it has served all governments worldwide during the past...

Documents

loop slide

whorl slide

small areas of friction

friction ridge patterns

loop pattern

corresponding epidermal

creation of minute ridges

fingerprint facts