Trace Evidence

1. Trace Evidence Any small pieces of material, naturally occurring or man-made.

2. Hair as Evidence • Abundant (very common) • Time will not change it • Easily lost • Mostly class evidence. • Used most often for sexual assault and violent assault

3. Hair as Evidence • Human hair is one of the most frequently found pieces of evidence at the scene of a violent crime – 31. It can provide a link between the criminal and the crime. Hair is not living tissue. (14.) • From hair one can determine (29.): • If the source is human or animal • Race (sometimes) • Origin of the location on the source’s body • Whether the hair was forcibly removed • If the hair has been treated with chemicals • If drugs have been ingested

4. Hair MorphologyThe Study of Structure and Form Parts of the hair • Shaft--part of the hair that sticks out of the skin • Root--lies below the epidermis • Follicle—organ from which the hair grows (source of DNA)

5. Three Layers of the Hair Shaft

6. Hair Shaft Composed of: • Cuticle—outside covering, made of overlapping scales • Cortex—inner layer made of keratin and imbedded with pigment; also contains air sacs called cortical fusi • Medulla—inside layer running down the center of the cortex

7. Hair Cuticle The cuticle is the outermost layer of hair which is covered with scales. Scales always point toward the tip of the hair. These scales differ between species of animals and are named based on their appearance. 25. Usually scale impressions are made in fingernail polish or similar material then they are viewed under the microscope.

8. Scale Types Mosaic Chevron

9. Rabbit chevron scales

10. Cat mosaic scales

11. Pectinate Imbricate

12. Human - Imbricate scales

13. Scale Types Petal Diamond Petal

14. Dog – petal scales

15. Hair Cortex The cortex is made up of spindle-shaped cortical cells that are aligned parallel to the length of the hair, giving the hair its shape. It has two major characteristics: • Melanin--pigment granules that give hair its color • Cortical fusi--air spaces, usually found near the root but may be found throughout the hair shaft

16. Hair Medulla The medulla is the central canal running through the hair core that is not always present. The medulla comes in different types and patterns. Types: • Continuous • Intermittent or interrupted • Fragmented • Absent--not present

17. Hair Medulla Patterns Uniserial Multiserial Vacuolated Lattice Amorphous(without a distinct pattern)

18. The index measures the diameter of the medulla relative to the diameter of the hair shaft. Medullary Index Medullary Index for human hair is generally less than 1/3. For animal hair, it is usually greater than 1/2.

19. Human medulla - continuous

20. Cat medulla

21. Rabbit medulla

22. Cow medulla

23. Deer medulla (not scales!)

24. Hair Root The hair root is the end in the follicle from which the hair grows. The length of hair grows 0.5 mm per day or 1 centimeter per month. There are three phases of hair growth: Anagen--hair that is growing up to 6 years; root has a flame shaped appearance and may have a follicular tag from which DNA may be obtained. Catagen--hair at rest for 2-3 weeks; has elongated appearance Telogen--hair growth is ended; has club shaped appearance.

25. Forcibly removed 13 &15. Follicular tag - Attached living tissue (only source of DNA) Forcibly removed Fallen out Anagen Forcibly removed hair shows damage and stretching of the root

26. Catagen Dormant, resting root gets longer and thinner.

27. Telogen Naturally shed hairs display club shaped root

28. Human root

29. Cat root

30. Animal vs. Human Cat Human Scale Structure Medullary index Medullary shape Hair Identification

31. Rabbit root

32. Electron Microscope Picture of Sheep Hair

33. Comparison Length Diameter Color intensity of pigments granules Dyed hair has color in cuticle and cortex Bleaching removes pigment and gives yellow tint Hair Identification

34. Origin of Human Hair Head hair- shows little diameter variation and more uniform distribution of pigment color Beard hair- coarse and have blunt tips due to being cut Pubic hair- short and curly, with wide variation in shaft diameter, or buckling, and have a continuous medullae Hair Identification

35. New Scissor Cut Tips of Hair • Blunt if recently cut • Rounded if cut and allowed to grow • Blackened or frayed show presenc of a flame • If broken end will be irregular Broken Broken Old Cut Razor Cut Burnt

36. Hair Shape Can be straight, curly or kinky depending on the cross-section, which may be round, oval or crescent-shaped Crescent moon (Kinky) Oval (Curly) Round (Straight)

37. Determination of Race Black/African hairs are kinky, containing dense, unevenly distributed pigments, diameter is elliptical and varies in size

38. Caucasian hairs are straight or wavy, with very fine to coarse pigments that are more evenly distributed, oval diameter which varies in size

39. Asian Hair Usually round constant diameter Thick cuticle Prominent medulla Pigments are dense and often arranged in large patches

40. Determination Age and Sex- only infant’s hair can be determined; sex cannot be determined Individualization - DNA analysis could provide a link from questioned hair to standard hair (follicular tag actually the source not the hair itself) Hair Identification

41. Collection of Trace Evidence These 3 methods can be done at the crime scene or in the crime lab. 1. Visual Inspection • Use naked eye or hand lens. • Evidence removed and packaged for later analysis • Use bright light and forceps to collec

42. Packaging from Visual Inspection • Small paper envelopes are bad (Holes allow small objects to escape). • Use small plastic bags, glass vial or paper using a druggist fold. • Double package. Label each package.

43. 36. Collection 2. Tape Lift • Clear tape is used. • Repeatedly apply tape to small area until most of the stickiness is gone. • Tape is folded back upon itself, taped to a glass slide or taped to a piece of plastic. • Put in separate labeled container. Be sure to document specific area covered.

44. Nozzle should be short and transparent. • Debris is collected on a filter or membraneSmall area is vacuumed. (Filters changed frequently) • Filters packaged in separate labeled container. (Be sure to document specific area covered) • Most improperly used method because it often results in the collection of a lot of irrelevant material. 3. Vacuuming

45. Collection of Hair Evidence • Questioned hairs must be accompanied by an adequate number of control samples. • from victim • possible suspects • others who may have deposited hair at the scene • Control Sample • 50 full-length hairs from all areas of scalp • 24 full-length pubic hairs

46. Hair Toxicology • Advantages: • Easy to collect and store • Is externally available • Can provide information on the individual’s history of drug use or of poisoning. • Collections must be taken from different locations on the body to get an accurate timeline.

47. Hair Toxicology • Napoleon died in exile in 1821. By analyzing his hair, some investigators suggest he was poisoned by the deliberate administration of arsenic; others suggest that it was vapors from the dyes in the wallpaper that did him in.

48. Comparison Microscope

49. Comparison Microscope • An optical bridge allows viewing of evidence side by side. • Useful for comparing bullets, fibers, hair…

50. Fibers Any small, elongated pieces of material used to manufacture cloth, carpet, paper, cardboard, rope, cord, or string.