Chapter 14 Criminalistics Fingerprints Chapter 14 Criminalistics

History of Fingerprinting Alphonse Bertillon in 1883 First systematic attempt at personal identification Anthropometry: system of precise body measurements. Included detailed descriptions of the subject Believed that dimensions of the human bone system remained fixed from the age of 20 until death. Full-length and profile photographs Problems? Accuracy of measurements were disproved by the William West Case

William Herschel Required natives in India to sign contracts with the imprint of their right hand Not sure if he noticed the differences in prints or was practicing a Hindu custom Did not publish any ideas until after Fauld

Henry Fauld (1880) Suggested skin ridge patterns were important for identification of criminals

History of Fingerprinting Francis Galton 1892: Published Finger Prints Described the anatomy of fingerprints and suggested methods for recording them Acknowledged that no two prints are alike and do not change throughout a lifetime Three pattern types Loops, Arches, and Whorls

Dr. Juan Vucetich Argentinian police officer First to devise a classification system for fingerprints Although modified, still widely used in Spanish-speaking countries

Sir Edmund Richard Henry Proposed another classification system in 1897 Most English-speaking countries use some form of this system to this day

Fundamental Principles of Fingerprints First Principle A fingerprint is an individual characteristic. No two fingers have yet been found to possess identical ridge characteristics Ridge Characteristics: The combination of details in the shapes and positions of ridges in fingerprints that make each unique; also called minutiae. Examples: bifurcation, enclosures, islands, ridge endings, short ridges, ridge crossings, deltas

Eye (enclosure or island) Minutiae: Names Visual Appearnce Double Bifurcation Island ridge (or short ridge) Spur (or hook) Trifurcation Eye (enclosure or island) Dot (or very short ridge)

Figure 14-1

Figure 14-2

Fundamental Principles of Fingerprints Second Principle A Fingerprint remains unchanged during an individual’s lifetime Formation of fingerprints: Developed during fetal development Hills (Ridges): raised portions of the epidermis Valleys (Grooves): lowered portions of the epidermis IT IS THE RIDGES THAT ARE INKED WHEN FINGERPRINTS ARE TAKEN

The three layers that compose skin are epidermis (outer layer), dermis (inner layer) and the shape of the dermal papillae which determine the form and pattern of the ridges at the surface of the skin.

It is impossible to change one’s fingerprint even though there have been numerous attempts. Serious injury can leave permanent scar. But it must penetrate 1 to 2 millimeters beneath the skin’s surface. Must damage the dermis

John Dillinger Tried to destroy fingerprints by using corrosive acid Prints taken at the morgue after his death were compared to prints taken from an earlier arrest showed that prints were unchanged and his efforts useless.

John Dillinger- before acid

John Dillinger prints- after acid

“Smiling Gus” Winkler Famous criminal of the 1920’s Had a strip down the center of his fingerprint surgically removed Efforts did not completely destroy ridge patterns

Before and After

Fundamental Principles of Fingerprints Third Principle Fingerprints have general ridge patterns that permit them to systematically classified.

Three Classes of Fingerprints Loops, Whorls, and Arches Loops: 65% of world’s population Whorls: 30-35% of world’s population Arches: 5% of world’s population

Loops

Whorls

Arches

Loop Patterns One or more ridges entering from one side of the print, recurving, and exiting from the same side

Types of Loop Patterns Ulnar Loop: loop opens toward little finger Radial Loop: loop opens toward the thumb Type Lines: pattern area of the loop surrounded by two diverging ridges Delta: the point directly in front of the diverging ridges—loops MUST have at least one delta Core: the center of pattern

Types of Whorl Patterns Four types of patterns Plain Whorl Central Pocket Loop Whorl Double Loop Whorl Accidental Whorl All whorl patterns must have type lines and a MINIMUM of two deltas.

Types of Whorl Patterns Plain and Central Pocket Loops Plain whorl and central pocket loops have AT LEAST one ridge that makes a complete circuit Ridge may be a spiral, oval, or any variant of a circle

Types of Whorl Patterns Plain Whorl: an imaginary line is drawn between TWO deltas and the spiral is crossed Central Pocket Loop: spiral is not crossed when imaginary line is drawn

Types of Whorl Patterns Double Loop: has two loops in one fingerprint Accidental Loop: has two or more patterns or is not classified into any other category

Types of Whorl Patterns Figure 14-6

Arch Patterns Plain arch: ridges entering one side of the fingerprint and exiting the other side Tented arch: this pattern rises sharply in the center

Arch Patterns Figure 14-7

Classification of Fingerprints The original Henry System converted ridge patterns on all 10 fingers into a series of numbers and letters arranged in the form of a fraction. Problem: It could only classify fingerprints up to 100,000 sets of prints so as collections grew, it became necessary to expand the capacity of the classification system.

FBI System In the US, the FBI expanded the classification capacity and these modifications are collectively known as the FBI System.

Using the FBI System, all fingerprint cards can be divided into 1,024 groups.

How the FBI System Works The following sequence can be used to classify fingerprints: R. Index R. Ring L. Thumb L. Middle L. Little 1 R. Thumb R. Middle R. Little L. Index L. Ring 1 16 8 4 2 0 Whorl Values Zeros are assigned for loops and arches Fraction gives individualized result for each person + + + + +

The presence or absence of the whorl pattern is the basis for determination of the primary classification. If a whorl pattern is found on any finger of the first pair, it is assigned a value of 16. On the second pair, a value of 8.

On the third pair, a value of 4. On the fourth pair, a value of 2. On the last pair, a value of 1. Any finger with an arch or loop patterns is assigned a value of 0.

Once all values are obtained, then 1/1 is added to the numerator and denominator. A fingerprint classification system cannot identify an individual, rather it provides a number of candidates that have similarities with the known set of prints. The identification must always be made by a final visual comparison of the suspects print’s and the file print’s ridge characteristics.

Problems with FBI System 25% of population falls into the 1/1 category Only useful when all 10 prints are available Cumbersome and Time Consuming to look through cards Often only one or two prints found at a crime scene

AFIS Automated Fingerprint Identification System Computer-scans and digitally encodes fingerprints based on minutiae of ridge endings and bifurications List of prints is generated then a fingerprint examiner confirms match

Benefits of AFIS Computer can make thousands of accurate fingerprint comparisons in a second Can filter out imperfections in latent prints found at a crime scene Suspect lists are generated faster and investigators can spend more time focusing on suspects

A Typical AFIS Matching Screen                                       A Typical AFIS Matching Screen

IAFIS Integrated Automated Fingerprint System Largest AFIS in the United States Contains nearly 50 million fingerprint records

What is included in IAFIS: Not only fingerprints, but corresponding criminal histories; mug shots; scars and tattoo photos; physical characteristics like height, weight, and hair and eye color; and aliases. The system also includes civil fingerprints, mostly of individuals who have served or are serving in the U.S. military or have been or are employed by the federal government. The fingerprints and criminal history information are submitted voluntarily by state, local, and federal law enforcement agencies.

Types of Crime Scene Prints Three Types: Visible Prints Plastic Prints Latent (Invisible) Prints

Visible Prints Can be seen with the naked eye Made by fingers touching a surface after ridges have been in contact with a colored material such as blood, paint, grease, ink, etc.

Plastic Prints Can be seen with the naked eye Made by ridge impressions left on a soft material such as putty, wax, soap, dust, wet paint surfaces, etc.

Latent Prints Cannot be seen with the naked eye Made by impressions caused by transfer of body perspiration or oils present on finger ridges to the surface of an object

Easiest surface to lift fingerprints: Hard, nonabsorbent surfaces (glass, mirrors, tile, painted wood): Powders or SuperGlue Fuming

Fingerprint Powders Applied with a camel’s hair or fiberglass brush Color of powder (usually gray or black) are chosen to contrast with surface color Powder adheres to oils and perspiration left by ridges Print can be lifted off the surface and preserved

                          

Magna Brush Can spread magnetic-sensitive powder to locate latent prints Does not have any bristles to come in contact with surface, meaning less chance of destroying or damaging a print

Ninhydrin Chemical used to develop prints on porous material such as paper Applied by dipping the object or spraying it with ninhydrin Safety: Do not inhale or get on your skin Reacts with amino acids in perspiration Developed prints appear purple-blue in color Prints appear within an hour or two and fully developed in 24-48 hours

Latent Prints recovered on paper with Ninhydrin

SuperGlue Fuming Used on nonporous surfaces such as metal, electrical tape, leather, and plastic bags Application: Evidence is placed in a fuming chamber and the cyanoacrylate is heated and covers the object Safety: Do not inhale or get on your skin, irritant to mucus membrane. Reacts with amino acids Produces a white latent print

Flashlight battery exposed to SuperGlue Fuming

Physical Developer (Silver Nitrate) Useful for detecting prints that cannot be found by other methods or on objects that have been wet at one time. Also on wood or styrofoam. Applied by dipping or spraying object with Silver Nitrate. Safety: Wear gloves and avoid contact with skin. Reaction: Chloride from salt in perspiration on the print combines with silver nitrate to form silver chloride. Print turns black or reddish brown under a UV light ***Application of Physical Developer washes away any protein that may be present and MUST be used last

Iodine Fuming Used to detect prints on paper, cardboard and unpainted surfaces (non-pourous) Iodine is a solid crystal that, when heated, is transformed into a gas through sublimation and reveals a latent print. Safety: Toxic to inhale or ingest Reaction: Iodine combines with carbohydrates in the print A brownish print forms but prints are not permanent and must be photographed immediately or fixed with starch solution, which can last about 1 month

Alternate Light Source Works because perspiration fluoresces under different wavelengths of light Can adjust the wavelength of light to be aimed through a fiber optic cable More commercially available than laser light setups

Alternative Light Source being used to detect latent prints

Preservation of Prints Once a latent print has been visualized it must be permanently preserved for future comparison and possible use in court as evidence. Photograph must be taken before and after further attempts to preserve the fingerprint.

Two Procedures to Follow: If object is small enough to be transported without destroying the print, it should be preserved in its entirety. Cellophane should cover the print to protect from damage

Prints on large immovable objects that have been developed with a powder can be best preserved by “lifting”. The most popular type of lifter is a broad adhesive tape similar to clear adhesive tape. When the powdered surface is covered with the adhesive side of the tape and pulled up, the powder is transferred on the tape. The tape is then placed on a properly labeled card that provides a good background contrast with the powder.

Digital Imaging When fingerprints are lifted from a crime scene, they are usually not in perfect condition. Using digital imaging, fingerprints can now be enhanced for the most accurate and comprehensive analysis.

Digital Imaging The process by which a picture is converted into a digital file

 Although digital imaging is undoubtedly an effective tool for enhancing and analyzing images, it is only as useful as the images it has to work with.