Forensic Science
Fingerprints
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 end
whorl- resemble bull’s-eye
loop- 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 Classifications
WHORLS
• whorls
– about 30% ALL
Fingerprints
–
–
–
–
Plain 24%
CP 2%
Double Loop 4%
Accidental <.01%
Advanced Classifications
ARCHES
• 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 AFIS
What 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’s
Can 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 chemicals
1930’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.