Fingerprinting

Forensic Science

Forensic Science

Fingerprinting

Is it a match?

• You will be given 2 prints.

• Compare the second print to this print.

• Can you determine if it is a match?

Major patterns

What are the distinguishing patterns of these fingerprints?

How would you describe them?

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Fundamental Principles of Fingerprints

An individual characteristic.

Unchanged during an individual’s lifetime.

Characteristic ridge patterns

Why do we have fingerprints?• Provides better grip

– Called dermal or friction ridges• ? Makes perspiration easier on a hairless

surface• ? Improves sense of touch

Skin • Epidermis (outer skin)

has 3 layers– Peridermal– Intermediate– Basal

• Dermis (under layer)– Amorphous fiber

• Basal Layer – new skin cells form

Prints form in the fetus

• Forms between the 10th – 17th week• Determined for life• Basal layer –

– Forms new skin cells – Grows faster than the upper layers and the dermis– Folds into interconnected ridges

Prints

• Natural secretions - water, oils, salt• Dirt

• Provide an impression on contacted surfaces

• Also on toes, soles of the feet, palms

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Fingerprint formation

Important Terms

• Dactyloscopy• Patent fingerprint• Plastic fingerprint• Latent fingerprint

• Epidermal• Basal layer• Dermis

• Arch• Loop• Whorl • Delta• Core• Minutia patterns

Resources

• http://finger-prints.com/index.html

• http://en.wikipedia.org/wiki/Fingerprint

• http://www.crimemuseum.org/library/forensics/fingerprints.html

• http://www.livestrong.com/article/287440-the-development-of-fingerprints-in-babies/

Major visual patterns

Loops 65% population

Whorls 30% population

Arches5% population

Classification of Fingerprints• Three basic patterns:

– Loop• 65%

– Whorls• 10-20%

– Arches• 5%

– Racial variations • African (more arches), European (more loops), Asians/Orientals

(more whorls)

Loop

A loop must have one or more ridges entering and exiting from the same side. Loops must have one delta.

Types Radial—opens toward the

thumb Ulnar—opens toward the

“pinky” (little finger) Which type of loop is this, if it

is on the right hand? Left hand?Delta

Whorl

Whorls have at least two deltas and a core.

Four Groups Plain Central Pocket Double Loop Accidental

Plain Whorl

Whorl

• Central Pocket

Whorl

• Double loop

Whorl

• Accidental

Arch

• Friction ridges that enter on one side of the finger and cross to the other side while rising upward in the middle.

• They do NOT have type lines, deltas, or cores.

Types

Plain Tented

Identify each fingerprint pattern.

?A B

CD E

Right Hand

Left Hand

Left Hand

Right Hand

Right Hand

It’s time to makesome prints!

Avoid Partial Prints

GOOD PRINTGet as much of the top part of your finger as possible!

Henry-FBI Classification• Developed by Edward Henry• Allowed all sets of ten fingerprints in the

world to be divided into 1024 groups• Secondary and more complex classifications

were created to allow for more groups

Primary Classification

The Henry—FBI ClassificationBased on WHORLS

Each finger is given a point value

right left

Primary Classification

Assign the number of points for each finger that has a whorl and substitute into the equation:

right right left left left index ring thumb middle little + 1

right right right left left thumb middle little index ring +1

That number is your primary classification number

=

Individualization• Henry-FBI Classification

– Narrows into a group• Ridge Classification

– Uses minutiae to individualize fingerprints– In U.S. there are no legal requirements for # of

points– Criminal courts accept 8 to 12 points– 150-200 minutiae in a good rolled print

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Fingerprint Minutiae

Ridge Characteristics

Minutiae—characteristics of ridge patterns

Ridge ending Short ridge Dot or fragment Bifurcation Double bifurcation Trifurcation Bridge Island Enclosure Spur

Comparison

Can you identify the points?

Fingerprint Minutiae

How are fingerprints analyzed?

The Automated Fingerprint Identification System—a computer system for storing and retrieving fingerprints

Established in the 1970s

IAFIS—the FBI’s Integrated Automated Fingerprint Identification System, which is a national database of all 10-print cards from all over the country

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Latent Prints

Latent fingerprints Hidden Natural secretions of human skin Require development for them to become visible

Most secretions come from glands: Eccrine—largely water with both inorganic

(ammonia, chlorides, metal ions, phosphates) and organic compounds (amino acids, lactic acids, urea, sugars). Most important for fingerprints.

Apocrine—secrete pheromones and other organic materials.

Sebaceous—secrete fatty or greasy substances.

Developing Latent Prints

Requires substances that interact with secretions

Attempt more than one technique, done in a particular order so as not to destroy the print

Iodine Fingerprint

Ninhydrin Fingerprint

Cyanoacrylate Fingerprints

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Other Prints

Lips—several common patterns

Voice—electronic pulses measured on a spectrograph

Foot—size of foot and toes; friction ridges on the foot

Shoes—can be compared and identified by type of shoe, brand, size, year of purchase, and wear pattern

Other Prints

Lips—display several common patterns

Short vertical lines

Short horizontal lines

Crosshatching Branching

grooves

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Other Prints

Palm—friction

ridges can be

identified and may

be used against

suspects

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Other Prints

Footprints are taken at

birth as a means of

identification of infants.

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Other Prints

A man has been convicted of suffocating an eldery woman on the basis of earprint evidence. The assailant was caught after police matched the inprint of his ear on the victim’s window. Police believe that the thief put his ear to the window to listen for signs of anyone home.

Earprint catches murderer

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Other Prints, continued

Teeth—bite marks are unique and

can be used to identify suspects.

These imprints were placed in gum

and could be matched to crime

scene evidence.

Other Prints

The blood vessel patterns in the eye may be unique to individuals. They are used today for various security purposes.

Which fingerprints are matches?

Match the ones that are made by the same finger. In some cases, one print may appear two or three times.

Matching can be facilitated by digital enlarging and comparing cropped areas, or by enlarging with a photocopier and using a transparency overlay. A = G = S This one is interesting; there are three separate impressions of the same finger with some very unique features. B = no match C = no match D = no match E = TF = J H = RI = no match K = O L = no matchM = P N = Q

Case Study: Madrid Bombings. Comparison of fingerprints

Mayfield prints Prime suspect