FORENSIC SCIENCE Prints - PowerPoint PPT Presentation

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  2. PrintsDactyloscopy: the study of fingerprints • Making Prints • Rolling prints • Modus Operandi--primary identification number • Lifting Prints • Black, white and fluorescent powder • Chemicals--ninhydrin, iodine, silver nitrate, cyanoacrylate • Other Types of Prints • Palm, lip, teeth, eye, ear, voice, shoe and feet prints

  3. What is a Fingerprint? • Skin has an outer layer (epidermis) which has ridges projecting inward, and an inner layer (dermis) which has projections pressing into the spaces between ridges • A fingerprint is a pattern made by the friction ridges, which is left behind due to sweat and oil that sticks to them. • Fingerprints form during the fetal stage of development.

  4. Fundamental Principlesof Fingerprints • A fingerprint is an individual characteristic. • A fingerprint will remain unchanged during an individual’s lifetime. • Fingerprints have general characteristics ridge patterns that permit them to be systematically classified.

  5. Ridge Characteristics Minutia--lines of the fingerprint • ridge ending • bifurcation • short ridge • dot or island • enclosure



  8. 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. Types • Plain- the arch is mild • Tented- the arch is spiked upward

  9. Plain arch

  10. Tented arch

  11. Loop A loop must have one or more ridges entering and exiting from the same side it began. Loops must have one delta (a“Y” pattern from diverging ridges) Types • Radial--opens toward the thumb • Ulnar--opens toward the “pinky” (little finger) Which type of loop is this, if on the right hand? Left hand?

  12. Whorl A Whorl has a minimum of 2 deltas. Types • Plain- 2 symmetric deltas and a complete ridge circuit (circular in pattern) • Central Pocket- 2 asymmetric deltas, one side appears to be stretched • Double Loop- 2 loops and 2 deltas • Accidental- a whorl that does not fit the 3 above pattern types Plain whorl

  13. Central Pocket Whorl

  14. Double Loop (whorl)

  15. Accidental whorl

  16. Human population fingerprint distribution • Loops: 65% • Whorls: 30% • Arches: 5%

  17. Primary Identification Numbers- NOTE: fix this slide in your packet Fingers are numbers 1 through 10 starting with the thumb on the right hand and continuing through with the thumb on left hand. Each finger is then given a point value as seen in the chart below. 1. right 2. right 3. right 4. right 5. right thumb index middle ring little 16 16 8 8 4 6. left 7. left 8. left 9. left 10.left thumb index middle ring little 4 2 2 1 1

  18. Primary Identification (cont)NOTE: fix this slide in your packet Set up a ratio of even numbered fingers over odd numbered, adding one in both the numerator and denominator. 2. right 4. right 6. left 8. left 10. left index ring thumb middle little 16 8 4 2 1 1 1 + 16 8 4 2 1 1. right 3. right 5. right 7. left 9. left thumb middle little index ring

  19. Fingers 2 8 2 1 16 8 4 1 16 4

  20. Latent Prints Latent fingerprints are those that are “hidden” and are not visible to the naked eye. These prints consist only of the natural secretions of human skin and require treatment to cause 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) • Apocrine--secrete cytoplasm and nuclear materials • Sebaceous --secrete fatty or greasy substances.

  21. Lifting Latent Prints Developing a print requires chemicals that react 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.

  22. Iodine Fingerprint

  23. Ninhydrin Fingerprint

  24. Lifting Latent Prints (cont) • Ninhydrin--reacts with amino acids to produce a purple reaction. • Silver nitrate--react with chlorides 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. It was first used by the FBI in 1978. Since lasers can damage the retina of the eye, special precautions must be taken and a filter used.

  25. Cyanoacrylate Fingerprints

  26. Other Prints • Ears--shape, length and width • Face--pictures being used in Florida to find criminals • Voice--electronic pulses measured on a spectrograph • Feet--size of foot and toes; lines of the feet • Shoes--can be compared and identified by type of shoe, brand, size and year of purchase

  27. Other Prints Palm--lines can be identified and may be used against suspects.

  28. Other Prints Foot Prints are taken at birth as a means of identification for infants.

  29. Other Prints The study of lip-prints is called cheiloscopy Lips--display one of five common patterns • Short vertical lines • Long vertical lines • Rectangular lines that may crisscross • Diamond • Branching

  30. Other Prints • The use of lip prints is not yet firmly established in our courts. • Two ways to potentially use lip prints: • 1- print patterns for identification • 2- chromatography to match lipstick marks

  31. 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.

  32. Other Prints The blood vessel patterns may be unique to individuals. They are used for today various security purposes.

  33. “FINGERED”Crazy Criminals A New Jersey resident phoned police after finding her back door slightly ajar with a muddy palm print on the glass. When the officer questioned the woman, it was determined that she had been gardening. When he compared her hand with the lifted print, he had a match!!