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Introduction to Forensic Science


Introduction to Forensic Science Fingerprints and Biometrics Alphonse Bertillon (April 23, 1853 February 13, 1914) was a French law enforcement officer and ... – PowerPoint PPT presentation

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Title: Introduction to Forensic Science

Introduction to Forensic Science
  • Fingerprints and Biometrics

Alphonse Bertillon
  • (April 23, 1853February 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

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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 suspectsand which
    recorded the information on standardized cards in
    orderly files.

Bertillon's system was based on five primary
  • 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
  • Bertillons 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 Vucetichs 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

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)

  • Once fingerprints are recorded, a system is
    required to describe and place them in logical
  • Different classification systems
  • English-speaking countries use system created by
    Sir Edward Richard Henry.
  • This system has been modified by the FBI in the

Henry System of Classification
Fingers arranged in pairs R Index R Ring
L Thumb L Middle L Little

R Thumb R
Middle R Little L Index
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 0
0 1 17 0 8
0 0 0 1
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
  • 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
  • The study of methods for uniquely recognizing
    humans based upon one or more intrinsic physical
    or behavioral traits.

Evaluating Biometrics Characteristics
  • Universality each person should have the
  • Uniqueness is how well the biometric separates
    individually from another.
  • Permanence measures how well a biometric resists
  • Collectability ease of acquisition for
  • Performance accuracy, speed, and robustness of
    technology used.
  • Acceptability degree of approval of a technology.
  • Circumvention ease of use of a substitute.

Classification of minutiae
  • Minutiae are basically ends and bifurcations of
    the ridge lines that comprise a fingerprint
  • Valleys are the preferred choice to trace in

Marked Minutiae
Fingerprint Matching Process
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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
  • 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 FBIS Integrated Automated
    Fingerprint Identification System (IAFIA), a
    national on-line fingerprint and criminal history
    database with identification and response

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 live-scan
    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

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 McKies 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

  • 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 IAFISIntegrated Automated
    Fingerprint Identification System.
  • The FBI initially called the match "100 percent
    positive" and an "absolutely incontrovertible

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
  • 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

Validity of fingerprinting as an identification
  • 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.

  • 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
  • Any physical or occupational defects of the
    person making the print
  • How the object on which the prints appear was
  • 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

  • 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 (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 --gt 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!
Alternate Light Source
Latent Print Development Methods
  • Traditional powders
  • Fluorescent Powders
  • Chemicals
  • Cyanoacrylate of superglue fuming
  • Visualization under
  • Laser
  • Alternative light
  • Ultraviolet illumination

Locating Prints
  • Crime Scene Technician
  • This technician is using powder to develop latent
  • Technicians often wear protective equipment
  • Several points can be seen

(Courtesy Nassau County, New York, Police
Superglue Fuming Chamber
  • is used to process the inside and the outside of
    the car.
  • is more efficient for processing larger objects.

(Courtesy Sirchie)
Measurement Comparison Authentication
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 wasnt me.

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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
  • 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 _at_ 10-4 false accept rate
  • 0.90 true accept rate _at_ 10-2 false accept rate.
  • The most accurate fingerprint system, using
    operational quality single fingerprints
  • 0.994 true accept rate _at_ 10-4 false accept rate
  • 0.999 true accept rate _at_ 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
  • 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

Creating a Database
  • Eight major tattoo classes Human, Animal, Plant,
    Flag, Object, Abstract, Symbol, Other 80
  • Scientists are developing automatic image based
    matching and retrieval of tattoo images

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Tattoos and Identification