Introduction to Forensic
Science
Fingerprints and Biometrics
Alphonse Bertillon
• (April 23, 1853—February 13, 1914) was a
French law enforcement officer and biometrics
researcher who created anthropometry, an
identification system based on physical
measurements.
• Anthropometry was the first scientific system
police used to identify criminals. Until this time,
criminals could only be identified based on
eyewitness accounts, which are known to be
unreliable.
Bertillon and the Mug Shot
• After the invention of photography, police began
to keep "rogues' galleries," disorganized
photographic collections of suspects and
convicts. They needed a way to retrieve
images and information quickly.
• In 1879, Alphonse Bertillon invented a method
that combined detailed measurement and
classification of unique features with frontal and
profile photographs of suspects—and which
recorded the information on standardized cards
in orderly files.
Bertillon's system was based on
five primary measurements
• head length
• head breadth
• length of the middle
finger
• the length of the left
foot
• the length of the "cubit"
(the forearm from the
elbow to the extremity
of the middle finger).
Bertillon Card
Bertillon created an early database
• Bertillon’s system combined photography and
measurement to create a record of unique identifiers
that could be used to track suspects, inmates, and
repeat offenders.
• Unique characteristics like tattoos and scars were also
recorded.
• His system depended on a complicated filing method
that cross-referenced a standardized set of identifying
characteristics, making the information retrievable.
• The identification process was entirely independent of
names and the final identification was confirmed by the
photographs included on the individual's card.
Bertillon Files
The Case of Will West
Will West's Bertillon Measurements
178.5; 187.0; 91.2; 19.7; 15.8; 14.8; 6.6; 28.2; 12.3;
9.7
William West's Bertillon Measurements
177.5; 188.0; 91.3; 19.8; 15.9; 14.8; 6.5; 27.5; 12.2;
9.6; 50.3
Fingerprint History
• 1880: Dr Henry Faulds published his first paper on the
subject in the scientific journal Nature in 1880. Returning
to the UK in 1886, he offered the concept to the
Metropolitan Police in London but it was dismissed.
• 1892: Sir Francis Galton published a detailed statistical
model of fingerprint analysis and identification and
encouraged its use in forensic science in his book Finger
Prints.
• 1892: Juan Vucetich, an Argentine police officer who had
been studying Galton pattern types for a year, made the
first criminal fingerprint identification. He successfully
proved Francisca Rojas guilty of murder after showing
that the bloody fingerprint found at the crime scene was
hers, and could only be hers.
Juan Vucetich’s Early Fingerprints
What Are Fingerprints?
• Friction ridges are found on skin of
– palms of hands
– palmar aspect of fingers
– soles of feet
– solar aspect of toes
• Designed by nature for firmer grip and
resistance to slippage
Skin Structure
•
•
•
•
Outer, surface layer of skin is epidermis
The inner layer of skin is the dermis
Between these two are the dermal papillae
Papillary pattern determines the form and
pattern of the friction ridges on skin
surface
Perspiration and oils are secreted
through glands in the skin
Uses of Fingerprints
• Fingerprints collected at a crime scene, or
on items of evidence from a crime, can be
used to identify suspects, victims and
other persons who touched a surface.
• Fingerprints can be used to identify a
corpse
• Fingerprints can be used to identify people
who might use aliases to disguise their
illegal intent.
First Principal: Fingerprints are
Unique
• Millions of prints taken over 90 years
• No two fingers have yet been found to
have identical ridge characteristics
(minutiae)
• Identical (monozygous) twins
– have same DNA
– have different fingerprints
Second Principal: Fingerprints are
Unchanged through Life
• Friction ridge pattern of skin develops
in utero (before birth)
• Pattern remains unchanged
throughout life
Do fingerprints remain unchanged?
• Impossible to do, but there has never
been a lack of trying
– John Dillinger-corrosive acid
• To change the pattern requires obliteration
of the dermal papillae (1- 2 mm deep)
• Attempts to destroy pattern causes
disruption, irreversibly adding more detail!
Left middle fingerprint
This permanent
scar irreversibly
changes the
fingerprint.
It starts near the
core of the loop
and passes to the
right of the screen.
Third Principal: General Patterns
allow systematic classification
• The 3 basic fingerprint patterns
– loops (60-65% of population of fingers)
– whorls (30-35% of fingers)
– arches (5% of fingers)
Classification
•Once fingerprints are recorded, a system
is required to describe and place them in
logical order
•Different classification systems
•English-speaking countries use system
created by Sir Edward Richard Henry.
•This system has been modified by the
FBI in the USA.
Henry System of Classification
Fingers arranged in pairs:
R Index
&
R Thumb
R Ring
&
R Middle
L Thumb
&
R Little
L Middle
&
L Index
L Little
&
L Ring
Whorl pattern on either finger of pair, scored as
16
8
4
2
1
Expressed as fraction. 1 added to numerator & denominator
e.g. Whorls on R Index & R Middle fingers
16
0
+
+
0
8
+
+
0
0
+
+
0
0
+
+
0
0
+
+
1 =
1
17
9
25% population are
1/1 (no whorls)
Three Categories of Fingerprints
• Plastic prints
– Created when the fingers touch against some material
such as putty
• Patent or visible prints
– Formed when the fingers are contaminated with such
things as ink or blood and touch a clean surface
• Latent/invisible prints
– Left on a surface from the small amounts of body oil
and perspiration that are normally found on friction
ridges
– Require enhancements to become visible
Fingerprints as Class Evidence
Biometrics
• The study of methods for uniquely
recognizing humans based upon one or
more intrinsic physical or behavioral traits.
http://en.wikipedia.org/wiki/Image:Biometrics_traits_classification.png
Evaluating Biometrics
Characteristics
• Universality each person should have the characteristic
• Uniqueness is how well the biometric separates
individually from another.
• Permanence measures how well a biometric resists
aging.
• Collectability ease of acquisition for measurement.
• Performance accuracy, speed, and robustness of
technology used.
• Acceptability degree of approval of a technology.
• Circumvention ease of use of a substitute.
http://en.wikipedia.org/wiki/Biometrics#Common_human_biometric_characteristics
Classification of minutiae
• Minutiae are basically ends and
bifurcations of the ridge lines that
comprise a fingerprint pattern.
• Valleys are the preferred choice to trace in
algorithms.
Minutiae
Marked Minutiae
Fingerprint Matching Process
Biometric system operations
• Capture: a physical or behavioral sample is
captured by the system during enrollment.
• Extraction: unique data is extracted from the
sample and a mathematical template is
created.
• Comparison: the mathematical code is then
compared with a new sample.
• Match/Non-match: the system then decides if
the features extracted from the new sample
are a match or a non-match.
Matching the fingerprint
• Most automatic systems
for fingerprint
comparison are based on
minutiae matching.
• The loop is the most
common.
• The loop is easy to
classify based on ridge
counting and it
constitutes 65% of all
patterns.
Traditional Fingerprint Identification
and Comparison
• In the past fingerprints taken from crime
scenes were classified, filed and searched
according to the Henry System
• Searching crime scene fingerprints against
a Henry System file was labor-intensive
• Technological advancement since the
1970s have allowed the creation of an
automated fingerprint identification
process
Automated Fingerprint
Identification System (AFIS)
• In the early 1970s, the FBI and the National
Bureau of Standards conducted feasibility
research for establishing an automated
fingerprint identification process
• AFIS allows law enforcement agencies to
conduct comparisons of applicant and suspect
fingerprints with literally thousands or millions of
file prints in a matter of minutes
Automated Fingerprint
Identification System (AFIS)
• AFIS has two major duties
– First is performing the functions of
classifying searching and matching prints
– Second is the storage and retrieval of
fingerprints data
• In July 1999, law enforcement agencies began
to have access to the FBI’S Integrated
Automated Fingerprint Identification System
(IAFIA), a national on-line fingerprint and
criminal history database with identification
and response capabilities
AFIS Fingerprint Comparison
• Latent prints can be
searched against a
file of 500,000 prints
in one half hour
• The system
produces a list of
possibles called a
candidate list
• Checked by a
qualified fingerprint
examiner
Automated Fingerprint
Identification System (AFIS)
• The local police agency must have a livescan fingerprint terminal. The agency may
then:
– Scan an arrestee's prints and mug shots
– Electronically transmit the prints, mug shots
and personal information to their state's
network for fingerprint checks
• The state agency then transmits the same
information to the FBI fingerprint
repository for matches
Fingerprints are not infallible
• Shirley McKie, a former policewoman was
acquitted of perjury. She was accused of
lying about a fingerprint at a murder trial.
The case stemmed from what was
allegedly Ms McKie’s thumb print, found at
the scene of a murder. She had denied
that the thumb print was hers, or that she
had even been in the room where it was
found.
• Expert witnesses backed the plea of innocence
and she was acquitted by a jury.
• The Chief Inspector of Constabulary, Mr William
Taylor, exonerated Ms McKie and concluded that
the Scottish Criminal Records Office (SCRO)
Fingerprint Bureau was “not fully effective and
efficient”.
• Taylor concluded that there should be a
move away from the current analysis
system, which seeks to match 16 points of
similarity between prints from a crime
scene and a suspect. Also highlighted the
need for improvements in training and
backed a centralised fingerprint service in
Scotland.
Brandon Mayfield and Madrid
bombing
• Brandon Mayfield is an American lawyer
identified as a participant in the Madrid bombing
based on a fingerprint match.
• The FBI Latent Print Unit ran the print collected
in Madrid and reported a match against one of
20 fingerprint candidates returned in a search
response from their IAFIS—Integrated
Automated Fingerprint Identification System.
• The FBI initially called the match "100 percent
positive" and an "absolutely incontrovertible
match".
Brandon Mayfield and Madrid
bombing
• The Spanish National Police examiners concluded the
prints did not match Mayfield, and after two weeks
identified another man who matched.
• The FBI acknowledged the error, and a judge released
Mayfield after two weeks in May 2004.
• In January of 2006, a U.S. Justice Department report
was released which faulted the FBI for sloppy work but
exonerated them of more serious allegations.
• The report found that misidentification was due to
misapplication of methodology by the examiners
involved: Mayfield is an American-born convert to Islam
and his wife is an Egyptian immigrant, not factors that
affect fingerprint search technology.
Validity of fingerprinting as an
identification method
• Fingerprint examination is an applied
science based upon the foundation of
biological uniqueness, permanence, and
empirical validation through observation.
• Reliability of fingerprint examination is
supported by the theories of biological
uniqueness and permanence, probability
modeling, and empirical data gained
through over one hundred years of
operational experience.
SWGFAST
• The mission of the Scientific Working Group on Friction
Ridge Analysis, Study and Technology (SWGFAST) is to
establish consensus guidelines and standards for the
forensic examination of fingerprints, palm prints and foot
prints.
• SWGFAST, established in 1995, is one of several
Scientific Working Groups (SWG).
• The Scientific Working Groups improve forensic science
practices and build consensus amongst federal, state,
and local forensic laboratories and practitioners.
• The SWGs are a focal point for discussion on key issues
in various forensic science disciplines and develop
guidelines and standards through consensus and general
acceptance. These guidelines and standards are then
published and are widely recognized by the forensic
community, the courts, and the forensic laboratory
accrediting bodies.
Collecting Fingerprint Data
• Fingerprint Data is much more common
than DNA data and is used to solve more
crimes.
• Fingerprint data can even be found years
later on evidence and used to solve cold
cases.
Conditions Affection Latent Print
Quality
• The surface on which the print is
deposited
• The nature of the material contaminating
the fingerprint
• Any physical or occupational defects of the
person making the print
• How the object on which the prints appear
was handled
• The amount of the transfer
Fingerprinting Technology
• Powder Techniques
– Used on non-absorbent surfaces
– Tipped or softly brushed on
• Various types
– Black powder (carbon)
– Grey powder (Aluminium dust)
– Magnetic-Sensitive Powder (Magnabrush)
– Fluorescent Powder (seen in UV light)
•
•
•
•
Powder is brushed on carefully
Excess is removed
Print lifted with broad adhesive tape/pad
Transferred by sticking tape onto card
Chemical Methods
• Iodine Fuming
• Ninhydrin
• DFO
• Silver Nitrate
• Physical developer
• Super Glue Fuming
Iodine
•
•
•
•
•
Oldest technique for latent prints
Iodine crystal sublimes in Fuming Cabinet
Iodine reacts with fatty oils or perspiration
Print fades rapidly
Fixed by spraying with starch solution
(blue)
Ninhydrin
• Ninhydrin (triketohydrindene hydrate)
• For latent prints on paper & porous
surfaces
• Easy to use & sensitive
• Sprayed on
• Prints appear 1-2 h
• weak prints up to 48 h, hastened by heat
Silver Nitrate
•
•
•
•
•
For Porous surfaces
paper, wood, cloth, brass
Article sprayed, brushed or dipped
AgNO3 + NaCl --> AgCl + NaNO3
AgCl is photosensitive, turns dark brown in
daylight or UV
• Blurs with time, recorded by photography
• Silver nitrate-based liquid reagent
• Useful on paper & porous surfaces
• may work when other methods have failed
– useful on previously wetted paper
Superglue Fuming
• Cyanoacrylate ester (Super Glue)
• Fuming by heat or NaOH in cabinet
• Fuming wand for use at scene (inside a
car)
• Non-porous surfaces
• metal, tape, leather, plastic
• White prints appear in a few hours
Fluorescence Techniques
•
•
•
•
Argon-ion Lasers
Alternate Light Sources
Colored filters & goggles required
Natural fluorescence by components of
perspiration and blood
• Fluorescent powders
• Fluorescent dyes
– ninhydrin + ZnCl
– Superglue + Rhodamine
Fluorescence can really work!
Before
After
Alternate
Light Source
Latent Print Development Methods
•
•
•
•
•
Traditional powders
Fluorescent Powders
Chemicals
Cyanoacrylate of superglue fuming
Visualization under:
– Laser
– Alternative light
– Ultraviolet illumination
3-11
Locating Prints
• Crime Scene Technician
This technician is using
powder to develop
latent prints
– Technicians often wear
protective equipment
– Several points can be
seen
(Courtesy Nassau County, New York, Police Department)
Superglue Fuming Chamber
• is used to process the
inside and the outside
of the car.
• is more efficient for
processing larger
objects.
(Courtesy Sirchie)
Biometrics
– Measurement
– Comparison
– Authentication
http://www.itl.nist.gov/div893/biometrics/
ID Proofing –Three Questions
• Is Joe Blow real person? Does a person named
Joe Blow with the claimed attributes exist?
—As a practical matter, if somebody lives for a while
under a name, that person exists
• Is the applicant that Joe Blow?
• Can Joe Blow later repudiate his registration?
– Can Joe later say, “Look, you may have registered
somebody as Joe Blow, but it wasn’t me.”
Patriot Act Mandates
• Develop and certify technology standard to
verify identity of foreign nationals applying for a
visa
– visa application at embassies and consulates
– background check against FBI criminal database and
DHS databases and “watch lists”
– ensure person has not received visa under a different
name
• Verify identity of persons seeking to enter the
U.S.
– verify that the person holding the travel document is
the same person to whom the document was issued
– airports, land border crossings, sea entry points
NIST Study Results
• The most accurate face systems:
– 0.72 true accept rate @ 10-4 false accept rate
– 0.90 true accept rate @ 10-2 false accept rate.
• The most accurate fingerprint system, using
operational quality single fingerprints:
– 0.994 true accept rate @ 10-4 false accept rate
– 0.999 true accept rate @ 10-2 false accept rate
• More fingerprints (1 vs 2-10) are more accurate
• Image Quality is critical
Face Recognition
Every face has numerous,
distinguishable landmarks, the
different peaks and valleys that
make up facial features.
These landmarks are defined as
nodal points. Each human face
has approximately 80 nodal
points. Some of these are:
Distance between the eyes
Width of the nose
Depth of the eye sockets
The shape of the
cheekbones
The length of the jaw line
These nodal points are measured
creating a numerical code, called
a faceprint, representing the
face in the database.
Tattoo Statistics
• Rising popularity (Harris Poll, July 2003):
• 16% of the adults in the US have at least one tattoo
• The highest incidence was found among Americans age
25 to 29 years (36%) and 30 to 39 years (28%)
• People living in the West (20%) are more likely to have
tattoos
• Democrats are more likely to have tattoos (18%) than
Republicans (14%) and Independents (12%)
• Approximately equal percentages of males (16%) and
females (15%) have tattoos
• Tattoos are getting bigger, more colorful and visible
Creating a Database
• Eight major tattoo classes: Human,
Animal, Plant, Flag, Object, Abstract,
Symbol, Other; 80 subcategories
• Scientists are developing automatic image
based matching and retrieval of tattoo
images
Tattoos and Identification