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Chapter 4: Fingerprints

Chapter 4: Fingerprints. History. First fingerprints were discovered in clay pottery during the T’ang Dynasty Dactyloscopy : study of fingerprints. FINGERPRINTS. History. Alphonse Bertillion First systematic attempt at personal identification Bertillion system

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Chapter 4: Fingerprints

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  1. Chapter 4: Fingerprints

  2. History • First fingerprints were discovered in clay pottery during the T’ang Dynasty • Dactyloscopy: study of fingerprints FINGERPRINTS

  3. History • Alphonse Bertillion • First systematic attempt at personal identification Bertillion system • Relied on a detailed description of the subject • Combined with full length and profile photographs • System of precise body measurements called anthropometry FINGERPRINTS

  4. History • Francis Galton • 1892 • Classic textbook finger prints • At Galton’s insistence • British government adopted fingerprinting • Supplement to the bertillion system. • Next step • Creation of classification systems • Capable of filing many thousands of prints • Logical and searchable sequence. FINGERPRINTS

  5. WHY FINGERPRINTS? • The most positive means for identifying people. • Because no two fingers with identical ridge characteristics • Fingerprints form on a person before birth and remain unchanged until the body decomposes after death. Every fingerprint is unique!

  6. WHAT IS A FINGERPRINT? A fingerprint is a pattern comprised of ridges and valleys. A Ridge – is a high. A Valley – is a depression or low. Friction ridges are also found on our palms, feet and toes.

  7. Valley Ridge

  8. Fingerprint Principles • Individual characteristic • Because no two fingers with identical ridge characteristics • Remains unchanged during an individual’s lifetime • General ridge patterns that permit systematic classification FINGERPRINTS

  9. Anatomy of Fingerprints • Epidermis • Outer layer of the skin • Dermis • Inner layer of the skin • Dermal papillae • Layer of cells between the epidermis and dermis • Responsible for determining the form and pattern of the ridges on the surface of the skin

  10. Anatomy of fingerprints • Dermal papillae develop in the human fetus @ 3 months • Enlarge during growth

  11. Anatomy of fingerprints • Finger touches a surface • Perspiration • Oils from hairy portions of the body • Transferred onto surface • Leaves fingerprint FINGERPRINTS

  12. Fingerprint patterns • All fingerprints • divided into three classes • Loops • Arches • whorls L.A.W. FINGERPRINTS

  13. Loops • A loop must have one or more ridges entering from one side of the print, re-curving, and exiting from the same side. • If the loop opens toward the little finger, it is called an ulnar loop. • If the loop opens toward the thumb, it is called a radial loop.

  14. Loops Figure4.3  Loop pattern.

  15. Loops • Must have one delta FINGERPRINTS

  16. Whorls

  17. Whorls • Divided into four groups • Plain • Central pocket loop • Double loop • Accidental • All have a minimum of two deltas FINGERPRINTS

  18. Whorls • Plain whorl and central pocket loop have at least one ridge that makes a complete circuit • Double loop: two loops combined into one fingerprint • Accidental • Two or more patterns • Or pattern not covered by the other categories FINGERPRINTS

  19. Arches

  20. Arches • Least common of general patterns • Plain arches • Tented arches • Arches do not have deltas, or cores FINGERPRINTS

  21. Plain Arches • Ridges entering from one side of the print • Rising and falling • Exiting on the opposite side • Like a wave

  22. Tented Arches • Sharp up-thrust or spike • The ridges meet at an angle that is less than 90 degrees FINGERPRINTS

  23. Questions???

  24. FINGERPRINT IDENTIFICATION How are fingerprints compared? Fingerprints are compared by noting the ridge characteristics on two prints to determine whether or not they match. An identification is established when a number of these characteristics occupy the same relative position on the two prints.

  25. Fingerprints and a fingerprint classification schema involving six categories: (a) arch, (b) tented arch, (c) right loop, (d) left loop, (e) whorl, and (f) double loop. Critical points in a fingerprint,called core and delta, are marked as squares and triangles.

  26. FINGERPRINT IDENTIFICATION • Henry Classification system • Developed a method of classifying fingerprints. • modified by the FBI that allowed all set of 10 fingerprints in the world to be divided into 1024 groups. • Table 4.2 Frequency of fingerprints • Loops Whorls Arches • Ulnar radial plain other plain tented • 60% 5% 20% 10% 4% 1% • loops = 65% whorl=30% arches =5%

  27. Ending Ridge Eye or Enclosure Trifurcation “T” Junction Ridge Crossing Bifurcationor fork ShortRidge Row of Dots Dot RIDGE CHARACTERISTICS (Minutiae) COMMON OCCASIONAL RARE

  28. Ridge Characteristics Use these characteristics as points of identification when comparing fingerprint samples. The more points you can find in common, the better the match!

  29. 11 1 10 2 9 3 8 4 5 7 6 RIDGE CHARACTERISTICS MAGNIFIED Points 1, 2, 4, 5 are Ending Ridges Points 3 and 9 are Dots Points 8, 10, 11 are Bifurcations Point 6 is an Enclosure (ISLAND) Point 7 Short Ridge

  30. Review of fingerprint types

  31. Spike or “tent” Plain Arch Ridges enter on one side and exit on the other side. Tented Arches Similar to the plain arch, but has a spike in the center. Arches Arches are the simplest type of fingerprints that are formed by ridges that enter on one side of the print and exit on the other. No deltas are present.

  32. Loops Loops must have one delta and one or more ridges that enter and leave on the same side. These patterns are named for their positions related to the radius and ulna bones. Delta Ulnar Loop (Right Thumb) Loop opens toward right or the ulna bone. Radial Loop (Right Thumb) Loop opens toward the left or the radial bone. NOTE: On the left hand, a loop that opens to the left would be an ulnar loop, while one that opens to the right would be a radial loop.

  33. Whorls Whorls have at least one ridge that makes (or tends to make) a complete circuit. They also have at least two deltas. If a print has more than two deltas, it is most likely an accidental. Central Pocket Whorl Plain Whorl Draw a line between the two deltas in the plain and central pocket whorls. If some of the curved ridges touch the line, it is a plain whorl. If none of the center core touches the line, it is a central pocket whorl.

  34. Double Loop Whorl Accidental Whorl Double loop whorls are made up of any two loops combined into one print. Accidental whorls contain two or more patterns (not including the plain arch), or does not clearly fall under any of the other categories. Delta Delta Whorls – Part 2

  35. Identify each fingerprint pattern. ? A B Right Hand Left Hand C Right Hand E D Right Hand Left Hand

  36. Presenting Fingerprints as Evidence • No legal requirements on the number of points but generally the courts will accept 8 to 12 points of similarity as sufficient proof. • Fingerprints do not lie but human error might account to wrongful convictions.

  37. Types of PrintsVisible & Latent Prints

  38. Latent Prints • Invisible fingerprints • Finger touches a surface • Body perspiration and/or oils present • Transferred to that surface • Leaves impression FINGERPRINTS

  39. Visible Prints • Fingers touch a surface after contact with a colored material such as blood, paint, grease, or ink • Plastic prints: left on a soft material, such as putty, wax, soap, or dust • Little problem to the investigator FINGERPRINTS

  40. Visualizing Latent Prints

  41. Detecting Prints • Hard nonabsorbent surfaces • Glass, mirror, tile, painted wood • Developed by the application of a powder • Can be lifted by clear tape & examined • Porous surfaces • Papers, cardboard, and cloth, styrofoam, leather • Require treatment with a chemical FINGERPRINTS

  42. Ninhydrin • Reacts with amino acids left by finger • Produces a orange /purple color (Ruhemann’s purple) • Commonly used with paper and porous surfaces

  43. Iodine Fuming • Heat iodine crystals (produces iodine vapors) • Combine with latent prints (react w/ oils on finger) to make them visible • Iodine prints are not permanent • Will fade • Must photograph the prints immediately • Works best on porous paper.

  44. Silver nitrate • Reacts with the salt left from sweat in a dried print . • AgNO3 + NaClAgCl *converts to dark Ag2O • Turns prints brownish-purple

  45. Super Glue® • Most widely used method to develop latent prints • Best used on nonporous surfaces such as metals, glass, adhesive tapes and plastic. • Leaves a white, permanent impression • can be treated with powders or fluorescent dyes to create a sharper contrast. • 98 to 99 percent cyanoacrylate ester Super Glue fuming • Fuming chamber (for up to six hours) FINGERPRINTS

  46. Reflected UV Imaging System • RUlVIS • No chemicals or powder • Locate With light source • investigator develops the print in the most appropriate fashion FINGERPRINTS

  47. Powders • Powders, available in a variety of colors, can be applied with a brush or magnetic wand, and adhere to perspiration and/or body oils of the print.

  48. Other methods • Photograph

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