Forensic ScienceFingerprints

2013-14

Structure of Skin• Skin consists of:

– Inner layer—dermis – Outer layer—epidermis– Basal layer or papillary dermis in

between• New cells generate here

• Basal layer contains DERMAL PAPILLAE that push up on dermis to create ridges with intricate shapes (fingerprints)

– Dermal papillae-fingerlike projections

• Fingerprints begin forming near the 10th week of pregnancy– Remain unchanged except to

enlarge during growth

• Eccrine glands = sweat glands• Sebaceous glands = oil glands

what are fingerprints

• All fingers, toes, feet, and palms are covered in small ridges • Ridges help us grip objects• Fingers accumulate natural secretions and dirt

– Natural secretions = sweat (eccrine glands) and oils (sebaceous glands)

• Fingers leave secretions and dirt to create prints on objects we touch

• FINGERPRINT = ANY IMPRESSION LEFT ON ANY SURFACE THAT CONSISTS OF PATTERNS MADE BY THE RIDGES ON A FINGER

Interesting Fact

• No two fingerprints are exactly alike– Not even on identical twins!

Classifications of Fingerprints

arch- ridge pattern originates on one end and leaves on other endwhorl- resemble bull’s-eyeloop- ridge pattern originates on one side and returns in direction of origin

Terms to Know

• Core- a center of a loop or whorl

• Delta- a triangle ridge pattern with ridges that go in different direction above and below the triangle

Advanced ClassificationsWHORLS

• whorls– about 30% ALL

Fingerprints

– Plain 24%– CP 2%– Double Loop 4%– Accidental <.01%

Advanced ClassificationsARCHES

• ARCHES– About 5 % of all fingerprints

• Plain (no delta) 4%• Tented (delta) 1%

Types of Fingerprint Impressions

There are 3 types of prints that investigators look for at crime scenes:

1. Patent fingerprints—visible prints transferred onto smooth surfaces by blood, mud, or other liquids

2. Plastic fingerprints—indentations left in soft materials such as clay or wax

3. Latent fingerprints—made visible by dusting with powders or the use of chemicals

Fingerprint Identification and Matching

• Forensic examiners look for…– Core

(the center of a whorl or loop) – Deltas

(triangular regions near a loop)

• Ridge count – Counting from the core to the edge of the delta– Distinguishes one fingerprint from another

Fingerprint Identification and Matching

• Minutiae- Ridge characteristics found on fingerprint– Average fingerprint has as

many as 150 minutiae or ridge characteristics

– Same characteristics + same relative location to each other (orientation) = a match

– 12 points needed to be considered a match

Before IAFIS

• Fingerprints had to be compared manually with ten-cards on file by local and federal agencies (FBI)– Ten card- a form used to record and preserve a

person’s fingerprints– This process was extremely tedious and it could

take as long as three months to find a match.

IAFIS or AFISWhat is it?

• IAFIS = integrated automated fingerprint identification system– Computerized Program– Databank contains fingerprints of over 47 million people– Can search a set of ten fingerprints at incredible rate

• 500,000 in less than a second

– Uses algorithms or formulas to assign each possible match a score

– Usually takes about 2 hours to find possible matches– Possible matches with highest scores are then examined

by a trained fingerprint experts to determine final matches

Lifting Latent Fingerprints

• Latent Fingerprints- can’t be seen with the naked eye– Common method---dusting with carbon dust.

• Metal or magnetic powders may also be used and are less messy

• Tape can then be used to lift the print– Print is photographed before it is lifted.

Other methods to reveal latent prints

Fingerprint FAQ’sCan Fingerprints Be Altered?

o Can fingerprints be erased?

Only temporarily; they will grow back if removed with chemicals

Pineapple workers in cuba, dissolve fingerprints yet they come back

John Dillenger career felon tried to erase using chemicals1930’s

scarring remains yet diminishes with time

o Is fingerprint identification reliable?

Yes, but analysts can make mistakes

o Can computers perform matches in seconds? No, but the FBI’s Integrated Automated Fingerprint Identification System (IAFIS or AFIS) can provide a match in 2 hours

The Future of Fingerprinting

• New scientific methods are being explore to further improve fingerprint collection techniques– Example = Microsopic glass

• 3D and better resolution

• New scanning technologies – Yield detail in minute patterns– Reduce analytical mistakes– Analyze trace elements of objects on the skin

FAMOUS CASES• Dr. Martin Luther King

– James Earl Ray• Left blanket wrapped package outside front of empty nearby building• Fingerprint evidence left in white mustang, binoculars, rifle, and on beer cans

– Plea bargain of 99 yrs.» Conspiracy theories still exist

• Richard Ramirez aka “The Night Stalker”– 14 + killings, 5 + rapes– LA and Orange county– News frenzy led to heightened awareness and led to eyewitness

reporting of attempted break in with license plate number of stolen car

– Fingerprint evidence recovered from stolen car• Ramirez fingerprints were on file because of previous traffic violation

FAMOUS CASES

• FALSELY ACCUSED!– Brandon Mayfield

• Spain’s 911 in 2004• Converted Muslim and American Lawyer in Portland,

OR• Arrested on …

– Partial print showed 15 pts matching– Algerian later arrested after a few weeks of his custody

summary

• Fingerprints have long been used for identification, and in the mid-1800s were recognized as unique to each person.

• Three main groups include arches, whorls, and loops. – Several types of whorls– Arches can be plain or tented

• Basic analysis includes looking for cores and deltas and making a ridge count.

• Advanced techiques uses location and orientation of minutiae

summary

• Investigators search for patent, plastic, and latent prints.

• Dusting with powders or using special chemicals can make latent fingerprints visible.

• New developments may eliminate errors by analysts.