What are Fingerprints?

2. What are Fingerprints? • If a finger touches a surface, perspiration and oils from the body are transferred onto the surface, leaving an impression of the finger’s frictionridgepatterns. • Fingerprints may contain traces of any material found in perspiration including DNA and chemicals such as nicotine.

3. What are Fingerprints? • Friction ridges are found on skin in the following regions: • Palms of hands • Palmar aspect (palm-side) of fingers • Soles of feet • Solar aspect (sole-side) of toes • They exist to give firmer grip and resistance to slippage. • The number of ridges and their shape is largely determined by genes.

4. Skin Surface • Outer surface layer of skin is the epidermis. • The inner layer of skin is the dermis. • Between these two are the dermal papillae. • The papillary pattern determines the form and pattern of the friction ridges on skin surface.

5. Skin Surface • Each skin ridge is populated by a single row of pores that are openings for ducts leading from the sweat glands. • Perspiration is released and deposited on the surface of the skin through these pores.

6. Fingerprints are Unique • Dermatoglyphicsis the study of fingerprints. • No two fingers have yet been found to have identical ridge characteristics (minutiae). • Ridge pattern remains unchanged throughout life.

7. Fingerprints do not Change • Friction ridge pattern of skin develops in utero (before birth) due to uneven stresses in the different layers of the developing skin. • Identical (monozygous) twins • have the same DNA. • have different fingerprints.

8. Intentionally Altering Fingerprints • Very difficult to do, but there has never been a lack of trying. • Bank robber John Dillinger attempted to burn off his fingerprints with corrosive acid. They grew back. • Illegal immigrants and criminals sometimes undergo finger print plastic surgery. They can still be identified by palm prints and DNA. • To change the pattern requires obliteration of the dermal papillae (1- 2 mm deep). • Attempts to destroy the pattern can backfire and cause more unique details!

9. Types of Fingerprint Patterns There are 3 basic fingerprint patterns • loops (60-65% of population) • whorls (30-35%) • arches (5%)

10. Loops • Have ridges entering from one side of the print, turning, and leaving from the same side. • The pattern area of the loop is surrounded by two diverging ridges known as type lines. • The approximate center is called the core. • The ridge point nearest the type line divergence is known as the delta(capital greek letter Δ).

11. Loops • 65% of the population have loops. • All loops must have one delta. • If the loop opens toward the little finger then it is a ulnar loop. • If the loop opens towards the thumb then it is a radial loop.

12. Arches • In an arch, ridges enter from one side of the print and exit on the opposite side.

13. Arches • Arches are divided into two distinct groups: • plain arches • tetrarches or tented arches • The tetrarch consists of an upthrusted ridge in the center of the arch.

14. Whorls • All whorl patterns must have a core and at least two deltas

15. Special Loops • The double loop is made up of two loops combined into one fingerprint. • The pocked loophas a small circle at the core.

16. Other Patterns • An accidental pattern contains two or more patterns, but not the plain arch, and is not covered by other categories. • It may consist of a combination loop and plain whorl or loop and tented arch.

17. Types of Prints • Latent: hidden or invisible • Made by natural body secretions of the hands and fingers (perspiration & grease) • Requires dusting or other method to make visible • Patent: visible to the naked eye • Blood, ink, dirt, glass • Plastic: a 3-D fingerprint • Wet paint • Soft material like clay

18. Impressions and Prints • Impression • 3-D • in soft surface • often visible • Print • 2-D • transfer of skin perspiration, oils, or a foreign substance • usually latent

19. Powder Techniques • Used on non-absorbent surfaces • Tipped or very softly brushed on • Various types • Black powder (carbon) • Grey powder (Aluminum dust) • Magnetic-Sensitive Powder (Magnabrush) • Fluorescent Powder (seen in UV light)

20. Using Powder with a Brush • Powder is brushed on carefully with a twirling motion. • The excess powder is removed with the brush or a puffer bulb. • Prints are photographed in place before lifting. • Lift the print with broad adhesive tape. • Transfer the print by sticking tape onto a card or lifter.

21. Chemical Techniques • Iodine Fuming • Ninhydrin • DFO • Silver Nitrate • Physical developer • Super Glue Fuming

22. Iodine Fuming • Oldest technique for latent prints • Iodine crystal sublimes in Fuming Cabinet • Iodine reacts with fatty oils or perspiration (salts) • Print fades rapidly • Fixed by spraying with starch solution (blue)

23. Ninhydrin • Ninhydrin (triketohydrindene hydrate) • For latent prints on paper & porous surfaces • Interacts with amino acids in proteins in fingerprints • Easy to use & sensitive • Sprayed on • Prints appear in 1-2 hours, weak prints in up to 48 hours, hastened by heat.

24. Silver Nitrate • For Porous surfaces • paper, wood, cloth, brass • Article sprayed, brushed or dipped with the solution • AgNO3 + NaClAgCl + NaNO3 • AgCl is photosensitive, turns dark brown in daylight or UV. • Blurs with time, recorded by photography

25. Superglue Fuming • Cyanoacrylate ester (Super Glue) • Fuming by heat or NaOH in cabinet • Fuming wand for use at scene (inside a car) • Non-porous surfaces • metal, tape, leather, plastic • White prints appear in a few hours

26. Fluorescence Techniques • Argon-ion Lasers • Alternate Light Sources • Colored filters & goggles required • Natural fluorescence by components of perspiration and blood • Fluorescent powders • Fluorescent dyes • ninhydrin + ZnCl • Superglue + Rhodamine

27. Classification Systems • Once fingerprints are recorded, a system is required to describe and place them in logical order. • The most prominent system used before computer analysis was the Henry System created by Sir Edward Richard Henry and AzizulHaquein the late 19th century. • The Henry System is still included as part of many electronic systems and taught by the FBI.

28. Henry Classification System • The fingerprint records in this system are classified by broad characteristics. • This system reduces the effort needed to search through vast fingerprint collections. • All 10 fingers are put into groups of 2 with numerical weights assigned to each group

29. Henry Classification System

30. Henry Classification System • Each fingerprint is then analyzed. • If a whorl is present the value is recorded for that fingerprint. • If a whorl does not exist then zero is recorded for that fingerprint

31. Henry Classification System

32. Henry Classification System • Next, the Henry Classification Formula is used to find the grouping ratio. • The grouping ratio is a unique identifier for categorizing the particular type of fingerprint that the person has.

33. Henry Classification System • The Henry Classification Formula is: • The grouping ratio cannot be simplified. For example, 32/32 and 1/1 are both unique ratios.

34. Henry Classification System grouping ratio =

35. Fingerprint Points • The individuality of a fingerprint is determined by a careful study of its ridge characteristics (points). • Specific traits found in friction ridges are used to establish an identification by their relative location to each other. • The average finger has between 75 and 175 points of identification. • The palmar area has over 2000 points of identification.

36. Types of Points

37. Matching Points • For two points to match they must be at the same location on the fingerprint be the same type. • At crime scenes only partial prints are usually recovered, therefore a small number of ridge characteristics may be compared. • 16 matching characteristics have been suggested to establish the uniqueness of a print.

38. Fingerprint Records • Originally, fingerprint records were made with ink on paper cards. • Finger prints were rolled in ink and 4-finger and 2-thumb flat impressions were collected. • Cards can be scanned into modern databases. • The demand for improved systems and digital records has created a movement toward scanning to replace ink.

39. IAFIS • Integrated Automated Fingerprint Identification system (IAFIS) is used by the FBI to store digital prints. • It is the largest biometric database in the world, containing records for more than 100 million people. • When the automated process is finished the system generates a “hit” list • Possible matches then checked by expert • New original prints obtained for checking

40. What is included in IAFIS? • Each record may include: • Criminal history • Fingerprints • Mug shots • Scars and tattoos • Physical characteristics • height, weight, aliases, hair and eye color, race

41. Who submits data to IAFIS? • The system includes civil fingerprints, mostly of individuals who have served or are serving in the U.S. military or have been or are employed by the federal government. • The fingerprints and criminal history information are submitted voluntarily by state, local, and federal law enforcement agencies. • Employment background checks, some firearms purchases, and the US-VISIT program also provide information to the system.