1. C6: Fingerprint Analysis
Forensic Science: Fundamentals & Investigations, Chapter 6

2. Chapter 6 Fingerprints By the end of this chapter you will be able to:
discuss the history of fingerprinting
describe the characteristics of fingerprints and fingerprinting minutiae
explain when and how fingerprints are formed
describe what causes fingerprints to be left on objects
identify the basic types of fingerprints
describe how criminals attempt to alter their fingerprints
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Forensic Science: Fundamentals & Investigations, Chapter 6

3. Chapter 6 Fingerprints By the end of this chapter you will be able to:
determine the reliability of fingerprints as a means of identification
describe the Integrated Automated Fingerprint Identification System (IAFIS)
explain how fingerprint evidence is collected
describe the latest identification technologies
determine if a fingerprint matches a fingerprint on record
use the process of lifting a latent print
Forensic Science: Fundamentals & Investigations, Chapter 6

4. Historical Development
The oldest known documents showing fingerprints date from third century B.C. China.
In ancient Babylon (dating back to B.C.), fingerprints pressed into clay tablets marked contracts.
The earliest written study (1684) is Dr. Nehemiah’s paper describing the patterns he saw on human hands under a microscope, including the presence of ridges.
In 1788, Johann Mayer noted that the arrangement of skin ridges is never duplicated in two persons. He was probably the first scientist to recognize this fact.
Forensic Science: Fundamentals & Investigations, Chapter 6

5. Historical Development
5. Nine fingerprint patterns were described in by Jan Evangelist Purkyn.
6. Sir William Herschel (shown at the right), in 1856, began the collection of fingerprints and noted they were not altered by age.
7. Alphonse Bertillon created a way to identify criminal’s prints that was used in 1883 to identify a repeat offender.
8. In 1888, Sir Francis Galton (shown at the right), and Sir Edmund Richard Henry, developed the fingerprint classification system that is still in use in the United States.
Forensic Science: Fundamentals & Investigations, Chapter 6

6. Historical Development
9. In 1891, Iván (Juan) Vucetich improved fingerprint collection. He began to note measurements on identification cards, as well as adding all ten fingerprint impressions. He also invented a better way of collecting the impressions.
10. Beginning in 1896, Sir Henry (mentioned in the last entry on the previous slide), with the help of two colleagues, created a system that divided fingerprints into groups. Along with notations about individual characteristics, all ten fingerprints were imprinted on a card (called a ten card).
Forensic Science: Fundamentals & Investigations, Chapter 6

7. Old Method of Identification (pre-1990)
Could take up to three months to find a match
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8. What was he looking at? A ten card
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9. IAFIS Automated fingerprint identification service
links police forces internationally
Results within two hours
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10. AFIS Search large files for a set of prints taken from an individual
The Automated Fingerprint Identification System—a computer system for storing and retrieving fingerprints
Established in the 1970s, AFIS enables law enforcement officials 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 1990s, most large jurisdictions had their own system in place. The problem: A person’s fingerprints may be in one AFIS database 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
Forensic Science: Fundamentals & Investigations, Chapter 6

11. Fingerprints are possible because:
Fingers have unique ridge patterns
Fingers produce secretions
These secretions stick to surfaces
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12. Did You Know? Your fingerprints are hereditary They are totally unique
They will never change
They form in the dermal papillae and will always return even after scarring or burning
Forensic Science: Fundamentals & Investigations, Chapter 6

13. Did You Know?
Gloves do not necessarily keep you from leaving fingerprints
You can leave prints through surgical gloves
They can be turned inside out to produce a print also
Leather works this way too
Forensic Science: Fundamentals & Investigations, Chapter 6

14. Secretions from fingers include:
Oils
Salt
Water
Proteins
Forensic Science: Fundamentals & Investigations, Chapter 6

15. What Are Fingerprints?
All fingers, toes, feet, and palms are covered in small ridges.
These ridges are arranged in connected units called dermal, or friction, ridges.
These ridges help us get or keep our grip on objects.
Natural secretions plus dirt on these surfaces leave behind an impression (a print) on those objects with which we come in contact.
Forensic Science: Fundamentals & Investigations, Chapter 6

16. Your skin:
Forensic Science: Fundamentals & Investigations, Chapter 6

17. Formation of Fingerprints
An animal’s external tissue (skin) consists of (a) an inner dermis and (b) an outer epidermis.
The creation of fingerprints occurs in a special layer (the basal layer) in the epidermis where new skin cells are produced.
Fingerprints probably begin forming at the start of the 10th week of pregnancy.
Because the basal layer grows faster than the others, it collapses, forming intricate shapes.
Forensic Science: Fundamentals & Investigations, Chapter 6

18. Fingerprints are:
Visible on surfaces such as a drinking glass, mirror or other smooth, reflective surface Or
Invisible (called Latent) and have to be treated to be visible
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19. Fingerprint surfaces Practically any surface including: Wood Cardboard
Objects in water
Skin (neck, bruises elsewhere)
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20. Fingerprint Patterns Eight basic patterns recognized by the FBI
Ten basic details within the patterns
At least 12 identical points are necessary for a match
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21. Characteristics of Fingerprints
There are 3 general fingerprint distinctions:
ARCH WHORL LOOP
About 5% About 30% About 65% of the population
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22. Fingerprints include:
Loops
Whorls
Arches
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23. Characteristics of Fingerprints
Basic patterns can be further divided:
Arch patterns can be plain (4%) or tented (1%).
Whorl patterns can be central pocket (2%), double loop (4%), or accidental (0.01%).
Even twins have unique fingerprints due to small differences (called minutiae) in the ridge patterns.
Forensic Science: Fundamentals & Investigations, Chapter 6

24. Characteristics of an 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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25. Tented Arch Plain Arch
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26. Characteristics of a 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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27. Examples of Loop Patterns
Forensic Science: Fundamentals & Investigations, Chapter 6

28. Characterics of Whorls
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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29. Examples of Whorl Patterns
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30. Notice the scar
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31. Characteristics of Fingerprints
Forensic examiners look for the presence of a core (the center of a whorl or loop) and deltas (triangular regions near a loop).
A ridge count is another characteristic that distinguishes one fingerprint from another. The count is made from the center of the core to the edge of the delta.
Forensic Science: Fundamentals & Investigations, Chapter 6

32. Ridge patterns
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33. Ridge Patterns
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34. Comparison of Fingerprints
There are no legal requirements in the United States on the number of points required for a match. Generally, criminal courts will accept 8 to 12 points of similarity.
Forensic Science: Fundamentals & Investigations, Chapter 6

35. Types of Fingerprints
There are 3 types of prints that investigators look for at crime scenes:
Patent fingerprints are visible prints transferred onto smooth surfaces by blood or other liquids.
Plastic fingerprints are indentations left in soft materials such as clay or wax.
Latent fingerprints are not visible but made so by dusting with powders or the use of chemicals.
Forensic Science: Fundamentals & Investigations, Chapter 6

36. Latent Fingerprints
Can be treated with various powders to help see the ridge patterns better.
These powders include:
manganese dioxide
graphite
a trace of metals in them (like aluminum).
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37. Powders Gray for dark objects Black for light colored objects
Chalk dust can be used if viewed on a dark background
Prints can be ‘lifted’ off a surface using adhesive tape
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38. Latent prints can be visualized using
‘Superglue’ in a sealed chamber
Using iodine vapor in a sealed chamber
Forensic Science: Fundamentals & Investigations, Chapter 6

39. Fingerprint Forensic FAQs
How are latent fingerprints collected?
Forensic Science: Fundamentals & Investigations, Chapter 6

40. Developing Latent Fingerprints
Developing a print requires substances that interact with secretions, causing 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 with the background.
Iodine—fumes react with oils and fats to produce a
temporary yellow-brown color.
Forensic Science: Fundamentals & Investigations, Chapter 6

41. Developing Latent Prints, cont’d
Ninhydrin—reacts with amino acids to produce a purple color.
Silver nitrate—reacts with chloride to form silver chloride, a material that turns gray when exposed to light.
Cyanoacrylate—“superglue” 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.
Forensic Science: Fundamentals & Investigations, Chapter 6

42. Fingerprint Forensic FAQs
Can fingerprints be erased?
No, if, for example, they are removed with chemicals, they will grow back.
Is fingerprint identification reliable?
Yes, but analysts can make mistakes.
Is fingerprint matching carried out by computers in a matter of seconds?
No, but the FBI’s Integrated Automated Fingerprint Identification System (IAFIS or AFIS) can provide a match in up to 2 hours for the prints in its Master File.
Forensic Science: Fundamentals & Investigations, Chapter 6

43. A famous set of prints John Dillinger
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44. Other Prints: Ear Print
A man has been convicted of suffocating an eldery woman on the basis of earprint evidence. The assailant was caught after police matched the inprint of his ear on the victim’s window. Police believe that the thief put his ear to the window to listen for signs of anyone home.
Forensic Science: Fundamentals & Investigations, Chapter 6

45. The Future of Fingerprinting
New scanning technologies and digitally identifying patterns may eliminate analytical mistakes.
Trace elements of objects that have been touched are being studied to help with the identification of individuals.
To help with identification, other physical features such as eyes and facial patterns are also being studied.
Forensic Science: Fundamentals & Investigations, Chapter 6

46. 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.
Basic analysis includes looking for cores, deltas, and making a ridge count.
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.
Forensic Science: Fundamentals & Investigations, Chapter 6