1. Trace Evidence Part II

2. Summary Microscopic Analysis Types of Trace Evidence Glass Hair (fur)
Fibers
Paint
Soil
Gunshot Residue

3. Hair What is hair? What crimes are hair involved in?
How is hair collected?
How is hair analyzed in the lab?

4. What is hair? Natural fibers of animal origin
Trace > Hair
What is hair?
Natural fibers of animal origin
Terms: human = hair; animal = fur
Usually growing (live root)

5. What is hair? Cellular material in the hair shaft (mtDNA)
Trace > Hair
What is hair?
Cellular material in the hair shaft (mtDNA)
Good DNA in the hair root for forcibly removed hairs (STR)

6. What crimes are hairs involved in?
Trace > Hair
What crimes are hairs involved in?
Hairs are shed from people; can link a person to a crime scene.
Animal fur may also link a person to a crime scene.

7. How is hair collected? Visually by hand or with forceps.
Trace > Hair
How is hair collected?
Visually by hand or with forceps.
Possibly tape lift.
Packaged in sealed containers.

8. How is hair analyzed? Look at class characteristics (microscope):
Trace > Hair
How is hair analyzed?
Look at class characteristics (microscope):
Color
Medulla, Cortex, Cuticle

9. How is hair analyzed? Medulla: Line down middle of hair
Trace > Hair
How is hair analyzed?
Medulla:
Line down middle of hair
Species ID or human ID
Present, absent, or fragmented

10. How is hair analyzed? Cortex: Color of hair Species ID or human ID
Trace > Hair
How is hair analyzed?
Cortex:
Color of hair
Species ID or human ID
May contain pigment blotches
May contain air pockets

11. How is hair analyzed? Cortex: Humans = 1 color entire length
Trace > Hair
How is hair analyzed?
Cortex:
Humans = 1 color entire length
Animals = color can vary at root/middle/tip

12. How is hair analyzed? Cuticle: “Scales” on outside of hair
Trace > Hair
How is hair analyzed?
Cuticle:
“Scales” on outside of hair
Species ID only
Humans = imbricate

13. How is hair analyzed? (cuticle)
Trace > Hair
How is hair analyzed? (cuticle)
Procedure:
Put clear nail polish on slide.
Place hair in nail polish; wait to harden.
Remove hair; look at indentations in nail polish (microscope).

14. Fibers Fibers are very useful as trace evidence:
Vary widely in class characteristics
color, shape, chemical composition, etc.
Easily transferred from one source to another (carpets, clothes, etc.)
Significant persistence (won’t degrade)

15. How are fibers used as evidence?
Trace > Fibers
How are fibers used as evidence?
As with other trace evidence, fibers can be transferred to/from a person or objects linking them to one another.

16. How long do fibers persist?
Trace > Fibers
How long do fibers persist?
Most fiber evidence is lost (fall off) a short time after the transfer occurs.
The fibers that do remain will be persistent.

17. Fibers can be classified into three main categories:
Trace > Fibers
Fibers can be classified into three main categories:
Natural (animal, plant, mineral)
Manufactured
Synthetic

18. Natural Fibers: Found in nature Can be artificially colored or treated
Trace > Fibers > Natural
Natural Fibers:
Found in nature
Can be artificially colored or treated
Cotton
Wool
Hemp

19. Animal Fibers Wool - Hairs from sheep Silk - comes from silkworm
Trace > Fibers > Natural
Animal Fibers
Wool - Hairs from sheep
Most common of animal fibers
Hairs are spun to form thread
Silk - comes from silkworm
Spun as double filament (separated before use)
Because of length, doesn’t shed easily
Other Hairs from Animals

20. Plant Fibers Cotton - seed hairs of cotton plant
Trace > Fibers > Natural
Plant Fibers
Cotton - seed hairs of cotton plant
by far most common fiber (find almost everywhere)
Under microscope, fibers resemble twisted ribbon

21. Other Plant Fibers: Linen - stem fiber from flax plant
Trace > Fibers > Natural
Other Plant Fibers:
Linen - stem fiber from flax plant
Kapok - from seed hairs of kapok plant
Other fibers - Manila, hemp, sisal, jute

22. Mineral Fibers Asbestos - crystalline material
Trace > Fibers > Natural
Mineral Fibers
Asbestos - crystalline material
Used to be used for insulation
Fractures into thin rods that can get into your lungs; can kill you
Not used much anymore

23. Filament vs. Staple Filament: Long continuous fiber (like silk)
Trace > Fibers
Filament vs. Staple
Filament: Long continuous fiber (like silk)
Staple: Filament is cut into smaller pieces; staples are spun together to form thread (like cotton)

24. Manufactured Fibers Regenerated Fibers Example: Rayon
Trace > Fibers > Manufactured
Manufactured Fibers
Regenerated Fibers
Cellulose is dissolved, then resolidified to form the polymer fiber
Can occur in filament or staple form
Example: Rayon

25. Synthetic Fibers Man made Can also be filament or staple Examples:
Trace > Fibers > Synthetic
Synthetic Fibers
Man made
Can also be filament or staple
Examples:
Nylon and Polyester

26. Synthetic Fibers Acrylics More common as evidence
Trace > Fibers > Synthetic
Synthetic Fibers
Acrylics
More common as evidence
Usually in staple form
Staples spun together, similar to wool

27. Trace > Fibers > Analysis
Begin by identifying and comparing class characteristics for unknown sample (evidence) and known sample.
Known
Unknown

28. Fibers from rug in a van. Fibers found on victim.
Trace > Fibers > Analysis
Fibers from rug in a van.
Fibers found on victim.

29. Class characteristics
Trace > Fibers > Analysis
Class characteristics
Color: microscopic examination
Size: length and width can be measured
Shape: cross section is viewed

30. Class characteristics
Trace > Fibers > Analysis
Class characteristics
Refractive Index – n. The ratio of the speed of light in air or in a vacuum to the speed of light in another medium.
Other microscopic properties (PLM)

31. Class characteristics
Trace > Fibers > Analysis
Class characteristics
Chemical Composition: determined by advanced instrumentation

32. Threads, Yarn, Rope, Cordage
Trace > Fibers > Cordage
Threads, Yarn, Rope, Cordage
Smallest component is fibers (staple) twisted together to form thread or is a filament.
This thread can then be twisted with other threads to form a thicker thread (string, etc.)
This thicker cord can then be twisted with other thicker cords, etc.

33. Threads, Yarn, Rope, Cordage
Trace > Fibers > Cordage
Threads, Yarn, Rope, Cordage
Small cords or fibers twisted together to form larger cords
At each step, the number of cords can be counted.
At each step, the twist direction is either “S” or “Z”

34. Fiber
niso
nll n
Biref
MP (ºC) K1
1.518 to 1.528
1.544 to 1.551
1.505 to 1.516
0.035 to 0.039
Does not melt K2
1.777 to 1.877
2.050 to 2.350
1.641 to 1.646
0.200 to 0.710 K3
1.512 to 1.521
1.510 to 1.520
1.512 to 1.525 to
-0.005 K4
1.538 to 1.539
1.530 to 1.539 to
-0.002
192 – 210 K5
1.533 to 1.545
1.568 to 1.583
1.515 to 1.526
0.049 to 0.061
210 – 230 K6
1.540 to 1.541
1.577 to 1.582
0.056 to 0.063
250 – 264 K7
1.522
1.553
1.507
0.046
182 – 186 K8
1.535 to 1.539
1.568 to 1.574
1.518 to 1.522
0.050 to 0.052
133 – 138 K9
1.567 to 1.575
1.632 to 1.642
1.534 to 1.542
0.098 to 0.102
282 – 290
K10
1.474 to 1.478
1.474 to 1.479
1.473 to 1.477
0.002 to 0.005
245 – 260 Q
1.520
1.515
1.513
-0.003

35. Glass What is glass? What crimes are glass involved in?
How is glass collected?
How is glass analyzed in the lab?

36. What is glass? Made from fused inorganic materials
Trace > Glass
What is glass?
Made from fused inorganic materials
Amorphus; not crystalline (molecules not arranged)
Varies in elemental formula
Many shapes and colors

37. How is glass involved in crime?
Trace > Glass
How is glass involved in crime?
Small fragments can be used as trace evidence (link objects/people)
Crime scene reconstruction

38. Trace > Glass
How is glass collected?
For reconstruction, detailed photographs can be taken or the entire pane of glass is collected.

39. Trace > Glass
How is glass collected?
For trace evidence, usually visually collected with forceps and packaged in plastic bags.

40. Trace > Glass
For reconstruction:
Radial cracks
Concentric cracks

41. For reconstruction: Trace > Glass Concentric cracks Radial cracks

42. Determine the direction of projectile.
Trace > Glass
For reconstruction:
Determine the direction of projectile.
When looking at a radial section, conchoidal fractures point back to the origin of the break
Core usually on opposite side of the origin

43. Determine the order of projectiles when dealing with more than one.
Trace > Glass
For reconstruction:
Determine the order of projectiles when dealing with more than one. 2 1 3

44. Determine the order of projectiles when dealing with more than one.
Trace > Glass
For reconstruction:
Determine the order of projectiles when dealing with more than one. 2 1 3

45. Trace > Glass
For trace analysis:
Associate unknown glass found at the crime scene with known samples to determine the source.
Done with microscopic analysis
Color, curve, thickness, etc.
Refractive index: Determined by placing glass in oils of different refractive indexes

46. Trace > Glass
Refractive index:
Low relief = no outside line R.I. of glass and oil are similar
High relief = thick outside line (Becke line) R.I. of glass and oil are different

47. Paint What is paint? What crimes are paint involved in?
How is paint collected?
How is paint analyzed in the lab?

48. What is paint? Colored chemical coating Covers cars and houses
Trace > Paint
What is paint?
Colored chemical coating
Covers cars and houses

49. What is paint? Paint contains 3 things:
Trace > Paint
What is paint?
Paint contains 3 things:
Vehicle – binds components together
Pigment – gives paint color
Extenders – used to modify gloss, texture, opacity, etc.

50. What crimes are paint involved in?
Trace > Paint
What crimes are paint involved in?
Hit and Runs – paint from car left at scene
Other vehicular accidents
Home invasion – windows; on suspect

51. How is paint collected? Visually by hand or with forceps.
Trace > Paint
How is paint collected?
Visually by hand or with forceps.
Packaged in sealed containers.

52. How is paint analyzed? Possibly a physical match (jigsaw-like)
Trace > Paint
How is paint analyzed?
Possibly a physical match (jigsaw-like)
Associate the unknown paint with a known sample (class characteristics)

53. Chemical composition determined by FT-IR
Trace > Paint > Analysis
How is paint analyzed?
Chemical composition determined by FT-IR
Chemical “Fingerprint”

54. Paint can be in multiple layers
Trace > Paint > Analysis
Paint can be in multiple layers
Each layer is analyzed to determine its physical and chemical properties.

55. Soil What is soil? What crimes involve soil? How is soil collected?
How is soil analyzed in the lab?

56. What is soil? Mixture of animal and vegetable materials, and minerals
Trace > Soil
What is soil?
Mixture of animal and vegetable materials, and minerals
In many ways, soil has a unique composition in a given area.

57. What crimes involve soil?
Trace > Soil
What crimes involve soil?
Due to the widespread location of soil (earth), it can be used to associate people, objects, and scenes in numerous cases.

58. How is soil collected & analyzed?
Trace > Soil
How is soil collected & analyzed?
Collected in jars or vials.
Materials in soil are identified and quantified.
Analysis relies on soil composition being:
Consistent over time in one location
Different in different locations

59. Gun Shot Residue (GSR) What is gun shot residue (GSR)?
What crimes are GSR involved in?
How is GSR collected?
How is GSR analyzed in the lab?

60. Trace > Gun Shot Residue
What is GSR?
Mixture of materials that originate from the firing of a gun.
From the chamber
From the barrel

61. What is GSR? GSR will fall onto hands of person firing the gun.
Trace > Gun Shot Residue
What is GSR?
GSR will fall onto hands of person firing the gun.

62. What crime is GSR involved in?
Trace > Gun Shot Residue
What crime is GSR involved in?
Crimes with guns

63. How is GSR collected & analyzed?
Trace > Gun Shot Residue
How is GSR collected & analyzed?
Hand/glove/paw is swabbed
Analysis:
Elements barium and antimony are found in high levels.
Use powerful microscopy (SEM)
Use chemical tests (color change reactions)