1. FINGERPRINTS

2. Wednesday - 10/19/11 Objective: Do Now: Today:
To describe the characteristics of fingerprints
Do Now:
Are fingerprints considered class or individual evidence?
Today:
Last H-option Presentation
Fingerprinting

3. Thursday – 10/20/11 Objective: Do Now: Today:
To describe the characteristics of fingerprints.
Do Now:
Read “Unaltered Identity” on p. 132 of text book. Answer question:
Can fingerprints be altered? Explain.
Today:
Fingerprinting Notes
Ten cards

5. WHAT ARE FINGERPRINTS? Hands, feet have unique pattern of skin ridges
Skin is coated with mix of sweat and oils
Any time you touch a surface, a trace amount of sweat/oil is left behind

6. HOW DO THEY FORM? Form on a fetus in the womb
The “basal layer” of skin grows faster than the epidermis and the dermis, making it wrinkle in random patterns
Twins do NOT have identical prints
Genetics does NOT determine your exact prints

7. HISTORY
2000 BC: Ancient China & Babylon—fingerprints on clay tablets and official documents (used for ID…? We don’t know.)
1788: Johann Mayer observes that fingerprints are unique to each person
1879: Alphonse Bertillon, clerk at a police records office in Paris, uses fingerprints to identify a repeat- offender criminal

8. Types of Fingerprints
Patent Prints: visible prints (left because someone’s hand had blood, ink, etc. on it)
Latent Prints: hidden prints that become visible only when fingerprint powder or other special techniques are used. Composed of sweat and body oils.
Plastic Prints: fingerprint indentations left in a soft material such as clay or wax

9. WHAT TYPE IS THIS?
Latent
Plastic
Patent

10. WHAT TYPE IS THIS?
Latent
Plastic
Patent

11. WHAT TYPE IS THIS?
Latent
Plastic
Patent

12. WHAT TYPE IS THIS?
Latent
Plastic
Patent

13. AFTER DUSTING FOR PRINTS…

14. WHAT TYPE IS THIS?
Latent
Plastic
Patent

15. Reliability of Fingerprints
UNIQUE: No two identical fingerprints have ever been found. Remain same for entire life.
ALTERATION: Fingerprints grow back. (Story of John Dillinger, a famous gangster.) Scars don’t cover the whole print.
MISTAKES: Human error is the cause of fingerprint ID errors. (Case of Brandon Mayfield/Madrid bombing.)

16. Characteristics of Fingerprints
(Book pg 137 – you need to see pictures!)
Arches (5%)
Plain and Tented
Whorls (30%)
Plain, Central pocket loop, double loop, accidental
Loops (65%)
Delta—a triangular region near a loop
Core—the center of a loop or whorl
PURPOSE: categories provide quick way to eliminate suspects. They DO NOT give an individualized identification of one person.

17. PLAIN ARCH
No core
No delta
4% of population

18. TENTED ARCH No core Presence of a DELTA is what makes it “tented”
1% of population

19. PLAIN WHORL Has core – ridges go in complete circle around it
2 deltas; a line drawn between deltas will cut at least one of the circles around core
24% of population

20. CENTRAL POCKET LOOP WHORL
Core has ridges in complete circle
2 deltas
Line between the deltas DOES NOT cross circles around core
2% of population

21. DOUBLE LOOP WHORL Contains 2 loops (so 2 cores) 2 deltas
4% of population

22. ACCIDENTAL WHORL Has 2 or more deltas
Combines 2 or more other patterns (loops, whorls, arches) but is not a tented arch
0.01% of population

23. LOOP Has core, but the core has no complete circles around it 1 delta
65% of population

24. 1) WHAT TYPE? How many cores does it have, if any?
How many deltas does it have, if any?
Does a line between deltas cross core circles?

25. 2) WHAT TYPE? How many cores does it have, if any?
How many deltas does it have, if any?
Does a line between deltas cross core circles?

26. 3) WHAT TYPE? How many cores does it have, if any?
How many deltas does it have, if any?
Does a line between deltas cross core circles?

27. 4) WHAT TYPE? How many cores does it have, if any?
How many deltas does it have, if any?
Does a line between deltas cross core circles?

28. 5) WHAT TYPE? How many cores does it have, if any?
How many deltas does it have, if any?
Does a line between deltas cross core circles?

29. 6) WHAT TYPE? How many cores does it have, if any?
How many deltas does it have, if any?
Does a line between deltas cross core circles?

30. 7) WHAT TYPE? How many cores does it have, if any?
How many deltas does it have, if any?
Does a line between deltas cross core circles?

31. 8) WHAT TYPE? How many cores does it have, if any?
How many deltas does it have, if any?
Does a line between deltas cross core circles?

32. 9) WHAT TYPE? How many cores does it have, if any?
How many deltas does it have, if any?
Does a line between deltas cross core circles?

33. 10) WHAT TYPE? How many cores does it have, if any?
How many deltas does it have, if any?
Does a line between deltas cross core circles?

34. RIDGE COUNT Way to help individualize prints
Imagine a line from core to edge of delta
Count how many ridges are crossed

35. MINUTIAE This is where it gets real, folks!
Primary means of individualizing prints
Every print has about 150 minutiae
Need 8-15 for “match” (basis of computer matches)

36. Comparison of Minutiae

37. IAFIS
Integrated Automatic Fingerprint Identification System (was “AFIS” before going international and is often still called AFIS)
Computerized system that uses ridge counts and types/locations of minutiae to match fingerprints to the 50 million in the database
Matches take hours, not seconds!

38. Detection of Latent Prints
Dusting with powders
Spraying/applying ninhydrin
Exposing to cyanoacrylate fumes (superglue)
Spray or dip in silver nitrate
Expose to iodine fumes

39. DUSTING FOR PRINTS
Fine dusts (often charcoal) stick to the sweat and oils on prints
Works best on smooth, nonporous surfaces (plastic, smooth metal, polished wood, glass)
Colored dusts provide better contrast depending on surface
Excess dust blown away
Fingerprint is then photographed
Then “lifted” with tape and placed on a fingerprint collection card

40. Dusting - disadvantages
Messy; prints can be smeared by brush (magnetic dust and magnetic dust remover helps in some situations; fluorescent dusts and UV lamps help)
Doesn’t work on rough or porous surfaces (unfinished wood; paper; Styrofoam; leather)
Not as sensitive as other techniques (which means that some prints may be too faint to appear from dusting)

41. Iodine fuming
Gets prints from paper, cardboard, unpainted/unfinished wood (porous surfaces)
Solid iodine is heated in a vapor tent, producing iodine vapors (sublimation)
Iodine crystallizes on prints, forming a brownish color
It fades quickly unless sprayed with a starch solution
Not used much anymore – more toxic, less sensitive than other methods

42. Iodine fingerprint (photograph it or spray it with starch!)

43. After Image Adjustment…

44. Cyanoacrylate (superglue)
Gets prints that are on plastic, metal, or glass
Item is placed in a “vapor tent” (enclosed area to contain fumes). Superglue is heated to create fumes. Can take hours.
Reacts with amino acids & water and becomes a white solid (harder to see than other types)

46. Ninhydrin Best for getting prints off of paper
Paper is sprayed with a solution of ninhydrin in acetone or alcohol
Ninhydrin reacts with amino acids (proteins) in sweat and becomes purple-blue
Takes up to 24 hours for prints to appear; ninhydrin is toxic and flammable

47. Silver nitrate
Gets prints from paper, wood, Styrofoam (better at detecting faint prints than almost any other method)
Object sprayed or dipped in AgNO3
Chloride from salt in sweat reacts to become silver chloride (AgCl), a white compound
Silver chloride is black or reddish-brown under UV light
AgNO3 + NaCl  AgCl + NaNO3
Permanently damages the material—used as a last resort if other methods fail