0. Chapter 4: Fingerprints
“Fingerprints can not lie,
but liars can make fingerprints.”
—Unknown

1. Fingerprints Students will learn:
Why fingerprints are individual evidence.
Why there may be no fingerprint evidence at a crime scene.
How computers have made personal identification easier.
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2. Students will be able to:
Fingerprints
Students will be able to:
Define the three basic properties that allow individual identification by fingerprints.
Obtain an inked, readable fingerprint for each finger.
Recognize the general ridge patterns (loops, whorls, and arches)
Identify friction ridge characteristics and compare two fingerprints with at least ten points of identification.
Explain the differences among latent, plastic, and visible fingerprints.
Develop latent prints (make them visible) using physical and chemical methods.
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3. This is a really interesting video about fingerprints and credentials. You might want to send it to the list serve. 53min
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4. Historical Development
3rd century B.C. in China—oldest known documents
Ancient Babylon ( B.C.)—fingerprints pressed into clay tablets marked contracts
1684—Dr. Nehemiah’s paper describes the patterns on human hands, including the presence of ridges
1788—Johann Mayer noted that the arrangement of skin ridges is never duplicated in two persons
Forensic Science: Fundamentals & Investigations, Chapter 6

5. Historical Development
1823—Jan Evangelist Purkyn describes nine fingerprint patterns
1856—Sir William Herschel (right) began the collection of fingerprints and noted they were not altered by age
1883—Alphonse Bertillon created a way to identify criminals that were repeat offenders
Forensic Science: Fundamentals & Investigations, Chapter 6

6. Historical Development
1888—Sir Francis Galton (r) and Sir Edmund Richard Henry developed the fingerprint classification system still used in the US
1891—Iván (Juan) Vucetich collected all ten fingerprint impressions and noted measurements
1896—Sir Henry, with two colleagues, created a system that divided fingerprints into groups. All ten fingerprints are imprinted on a card (called a ten card) along with other notations
Forensic Science: Fundamentals & Investigations, Chapter 6

7. Example of a Ten Card
Forensic Science: Fundamentals & Investigations, Chapter 6

8. Fundamental Principles of Fingerprints
*A fingerprint is an individual characteristic.
*A fingerprint will remain unchanged during an individual’s lifetime.
Fingerprints have general characteristic ridge patterns that permit them to be systematically classified.
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9. *What Are Fingerprints?
All fingers, toes, feet, and palms are covered in small ridges
Ridges help us grip objects
Ridges are arranged in connected units called dermal, or friction, ridges
Fingers accumulate natural secretions and dirt
Fingers leave and create prints on objects we touch
Forensic Science: Fundamentals & Investigations, Chapter 6

10. Structure of Skin
Forensic Science: Fundamentals & Investigations, Chapter 6

11. Formation of Fingerprints
Skin consists of:
Inner layer—dermis
Outer layer—epidermis
Basal layer in between
Basal layer grows faster than the layers above and below it
Basal layer collapses and folds to form intricate shapes
Fingerprints begin forming near the 10th week of pregnancy
Forensic Science: Fundamentals & Investigations, Chapter 6

12. Ridge Characteristics
*Minutiae—characteristics of ridge patterns
Ridge ending
Short ridge
Dot or fragment
Bifurcation
Double bifurcation
Trifurcation
Bridge
Island
Enclosure
Spur
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13. Fingerprint Minutiae
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14. *Characteristics of Fingerprints
There are 3 general fingerprint distinctions:
ARCH
About 5%
WHORL
About 30%
LOOP
About 65%
of the population
Forensic Science: Fundamentals & Investigations, Chapter 6

15. Characteristics of Fingerprints
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
Forensic Science: Fundamentals & Investigations, Chapter 6

16. Arch
An arch has friction ridges that enter on one side of the finger and cross to the other side while rising upward in the middle. They do NOT have type lines, deltas, or cores.
Types
Plain
Tented
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17. *Characteristics of Fingerprints
Forensic Science: Fundamentals & Investigations, Chapter 6

18. Loop
A loop must have one or more ridges entering and exiting from the same side. Loops must have one delta.
Types
Radial—opens toward the thumb
Ulnar—opens toward the “pinky” (little finger)
Which type of loop is this, if it is on the right hand? Left hand?
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19. Whorl
A plain or central pocket whorl has at least one ridge that makes a complete circuit. A double loop is made of two loops. An accidental is a pattern not covered by other categories. Whorls have at least two deltas and a core.
Types
Plain
Central Pocket
Double Loop
Accidental
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20. Characteristics of Fingerprints
Forensic Science: Fundamentals & Investigations, Chapter 6

21. Characteristics of Fingerprints
Basic patterns can be further divided:
Arch patterns:
4% plain
1% tented
Whorl patterns:
2% central pocket
4% double loop
0.01% accidental
Even twins have unique fingerprints
Forensic Science: Fundamentals & Investigations, Chapter 6

22. Comparison
*There are no legal requirements in the United States on the number of points. Generally, criminal courts will accept 8 to 12 points of similarity.
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23. Latent Prints
*Latent fingerprints are those that are not visible to the naked eye. These prints consist of the natural secretions of human skin and require development for them to become visible.
Most secretions come from three glands:
Eccrine—largely water with both inorganic (ammonia, chlorides, metal ions, phosphates) and organic compounds (amino acids, lactic acids, urea, sugars). Most important for fingerprints.
Apocrine—secrete pheromones and other organic materials.
Sebaceous—secrete fatty or greasy substances.
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24. *Types of Fingerprints
There are 3 types of prints that investigators look for at crime scenes:
Patent fingerprints—visible prints transferred onto smooth surfaces by blood or other liquids
Plastic fingerprints—indentations left in soft materials such as clay or wax
Latent fingerprints—made visible by dusting with powders or the use of chemicals
Forensic Science: Fundamentals & Investigations, Chapter 6

25. Developing Latent Prints
Developing a print requires substances that interact with secretions that cause the print to stand out against its background. It may be necessary to attempt more than one technique, done in a particular order so as not to destroy the print.
Powders—adhere to both water and fatty deposits. Choose a color to contrast the background.
Iodine—fumes react with oils and fats to produce a temporary yellow brown reaction.
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26. Developing Latent Prints
Ninhydrin—reacts with amino acids to produce a purple color.
Silver nitrate—reacts with chloride to form silver chloride, a material which turns gray when exposed to light.
Cyanoacrylate—“super glue” fumes react with water and other fingerprint constituents to form a hard, whitish deposit.
In modern labs and criminal investigations, lasers and alternative light sources are used to view latent fingerprints. These were first used by the FBI in Since lasers can damage the retina of the eye, special precautions must be taken.
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27. Iodine Fingerprint
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28. Ninhydrin Fingerprint
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29. Cyanoacrylate Fingerprints
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30. National treasure finger print
1:28
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31. Fingerprint Forensic FAQs
How are latent fingerprints collected?
Forensic Science: Fundamentals & Investigations, Chapter 6

32. Fingerprint Forensic FAQs
Can fingerprints be erased?
Only temporarily; they will grow back if removed with chemicals
Dillinger:
Is fingerprint identification reliable?
Yes, but analysts can make mistakes
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
Forensic Science: Fundamentals & Investigations, Chapter 6

33. *Other Prints Ears—shape, length and width
Voice—electronic pulses measured on a spectrograph
Foot—size of foot and toes; friction ridges on the foot
Shoes—can be compared and identified by type of shoe, brand, size, year of purchase, and wear pattern.
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34. *Other Prints
Palm—friction ridges can be identified and may be used against suspects.
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35. *Other Prints
Footprints are taken at birth as a means of identification of infants.
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36. *Other Prints Lips—display several common patterns
Short vertical lines
Short horizontal lines
Crosshatching
Branching grooves
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37. *Other Prints
Teeth—bite marks are unique and can be used to identify suspects. These imprints were placed in gum and could be matched to crime scene evidence.
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38. *Other Prints
The blood vessel patterns in the eye may be unique to individuals. They are used today for various security purposes.
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39. *AFIS
The Automated Fingerprint Identification System - a computer system for storing and retrieving fingerprints
Began in the early 1970’s to:
Search large files for a set of prints taken from an individual
Compare a single print, usually a latent print developed from a crime scene
By the 1990’s most large jurisdictions had their own system in place. The problem - a person’s fingerprints may be in one AFIS but not in others
IAFIS—the FBI’s Integrated Automated Fingerprint Identification system which is a national database of all 10-print cards from all over the country
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40. *Biometrics
*Use of some type of body metrics for the purpose of identification. (The Bertillon system may actually have been the first biometry system.)
Used today in conjunction with AFIS
Examples include retinal or iris patterns, voice recognition, hand geometry
Other functions for biometrics—can be used to control entry or access to computers or other structures; can identify a person for security purposes; can help prevent identity theft or control social services fraud.
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41. More about Prints
For additional information about prints and crime, check out Court TV’s Crime Library
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