1. 11-1 ©2011, 2008 Pearson Education, Inc. Upper Saddle River, NJ 07458 FORENSIC SCIENCE: An Introduction, 2 nd ed. By Richard Saferstein Trace Evidence l: Hairs and Fibers Chapter 11

2. 11-2 ©2011, 2008 Pearson Education, Inc. Upper Saddle River, NJ 07458 FORENSIC SCIENCE: An Introduction, 2 nd ed. By Richard Saferstein Introduction Hair is encountered as physical evidence in a wide variety of crimes. Although it is not yet possible to individualize a human hair to any single head or body through its morphology or structural characteristics, it still has value as physical evidence.

3. 11-3 ©2011, 2008 Pearson Education, Inc. Upper Saddle River, NJ 07458 FORENSIC SCIENCE: An Introduction, 2 nd ed. By Richard Saferstein Introduction When properly collected and submitted to the laboratory accompanied by an adequate number of standard/reference samples, hair can provide strong corroborative evidence for placing an individual at a crime scene.

4. 11-4 ©2011, 2008 Pearson Education, Inc. Upper Saddle River, NJ 07458 FORENSIC SCIENCE: An Introduction, 2 nd ed. By Richard Saferstein Hair Morphology Hair is an appendage of the skin that grows out of an organ known as the hair follicle.

5. 11-5 ©2011, 2008 Pearson Education, Inc. Upper Saddle River, NJ 07458 FORENSIC SCIENCE: An Introduction, 2 nd ed. By Richard Saferstein Hair Morphology The length of a hair extends from its root or bulb embedded in the follicle, continues into a shaft, and terminates at a tip end. It is the shaft, which is composed of three layers—the cuticle, cortex, and medulla —that is subjected to the most intense examination by the forensic scientist. –A hair in cross section is like a pencil - the medulla is the lead, the cortex is the wood and the cuticle is the paint covering the wood

6. 11-6 ©2011, 2008 Pearson Education, Inc. Upper Saddle River, NJ 07458 FORENSIC SCIENCE: An Introduction, 2 nd ed. By Richard Saferstein Hair Morphology Two features that make hair a good subject for establishing individual identity are –Resistance to chemical decomposition –Ability to retain structural features over a long period of time These features are attributed to the cuticle portion of the hair

7. 11-7 ©2011, 2008 Pearson Education, Inc. Upper Saddle River, NJ 07458 FORENSIC SCIENCE: An Introduction, 2 nd ed. By Richard Saferstein Hair Morphology The cuticle is the overlapping scale structure covering the exterior of the hair. –The scales always point towards the tip of the hair. –The scale pattern is useful in species identification.

8. 11-8 ©2011, 2008 Pearson Education, Inc. Upper Saddle River, NJ 07458 FORENSIC SCIENCE: An Introduction, 2 nd ed. By Richard Saferstein Hair Morphology Imbricate scales are overlapping and have no apparent pattern –Found in humans Coronal scales are symmetrical and overlap one another –Not usually found in humans Spinous scales are triangular in shape and protrude from the shaft –Not found in humans

9. 11-9 ©2011, 2008 Pearson Education, Inc. Upper Saddle River, NJ 07458 FORENSIC SCIENCE: An Introduction, 2 nd ed. By Richard Saferstein Cuticle and Cortex The cortex is the interior of the hair shaft contained within the protective layer of the cuticle. –Its major forensic importance is the fact that it is embedded with the pigment granules that impart hair with color. –The color, shape, and distribution of these granules provide the criminalist with important points of comparison among the hairs of different individuals.

10. 11-10 ©2011, 2008 Pearson Education, Inc. Upper Saddle River, NJ 07458 FORENSIC SCIENCE: An Introduction, 2 nd ed. By Richard Saferstein Medulla The medulla is a cellular column running through the center of the hair. –The medullary index measures the diameter of the medulla relative to the diameter of the hair shaft. For humans, the medulla generally occupies less than 1/3 the diameter of the shaft, For animals it is generally 1/2 or greater.

11. 11-11 ©2011, 2008 Pearson Education, Inc. Upper Saddle River, NJ 07458 FORENSIC SCIENCE: An Introduction, 2 nd ed. By Richard Saferstein Medulla The presence or appearance of a medulla varies greatly –From individual to individual –Among hairs of the same individual Not all hairs have a medulla, and when it is present, the degree of medullation can vary

12. 11-12 ©2011, 2008 Pearson Education, Inc. Upper Saddle River, NJ 07458 FORENSIC SCIENCE: An Introduction, 2 nd ed. By Richard Saferstein Medulla –The medulla may be continuous, interrupted, fragmented or absent.

13. 11-13 ©2011, 2008 Pearson Education, Inc. Upper Saddle River, NJ 07458 FORENSIC SCIENCE: An Introduction, 2 nd ed. By Richard Saferstein Medulla Human head hairs generally lack medullae or have fragmented ones; rarely show continuous medullation –Mongoloid race usually have head hairs with continuous medulla Most animals have medullae that are either continuous or interrupted

14. 11-14 ©2011, 2008 Pearson Education, Inc. Upper Saddle River, NJ 07458 FORENSIC SCIENCE: An Introduction, 2 nd ed. By Richard Saferstein Medulla The shape of the medulla can also give clues to its origin. –Humans (and many other animals) have a medulla that is nearly cylindrical –Cats have a medulla resembling a string of pearls –Members of the deer family show spherical cells occupying the medulla of the entire hair shaft

15. 11-15 ©2011, 2008 Pearson Education, Inc. Upper Saddle River, NJ 07458 FORENSIC SCIENCE: An Introduction, 2 nd ed. By Richard Saferstein Root The root and other surrounding cells in the hair follicle provide the tools necessary to produce hair and continue its growth. Human head hair grows in three developmental stages Anagen Catagen Telogen

16. 11-16 ©2011, 2008 Pearson Education, Inc. Upper Saddle River, NJ 07458 FORENSIC SCIENCE: An Introduction, 2 nd ed. By Richard Saferstein Root Anagen is the initial growth stage and may last up to six years. The root is attached to the follicle for continued growth, giving the root bulb a flame-shaped appearance –When pulled from the head, some translucent tissue surrounding the hair’s shaft near the root may be found. This is called a follicular tag. –By using DNA analysis on the follicular tag, the hair may be individualized.

17. 11-17 ©2011, 2008 Pearson Education, Inc. Upper Saddle River, NJ 07458 FORENSIC SCIENCE: An Introduction, 2 nd ed. By Richard Saferstein Root During the catagen phase, hair continues to grow, but at a decreasing rate which can last anywhere from 2-3 weeks. Roots typically appear elongated as the root bulb shrinks and is pushed out of the hair follicle

18. 11-18 ©2011, 2008 Pearson Education, Inc. Upper Saddle River, NJ 07458 FORENSIC SCIENCE: An Introduction, 2 nd ed. By Richard Saferstein Root The telogen phase occurs once hair growth ends. The root takes on a club-shaped appearance. Over 2-6 months, the hair is pushed out of the follicle, causing the hair to be naturally shed.

19. 11-19 ©2011, 2008 Pearson Education, Inc. Upper Saddle River, NJ 07458 FORENSIC SCIENCE: An Introduction, 2 nd ed. By Richard Saferstein Comparing Strands The cuticle is examined by making a hair mold and observed under a comparison microscope. The medulla is examined with an electron scanning microscope.

20. 11-20 ©2011, 2008 Pearson Education, Inc. Upper Saddle River, NJ 07458 FORENSIC SCIENCE: An Introduction, 2 nd ed. By Richard Saferstein Comparing Strands Upon finding hair at a crime scene, the first question that must be answered is whether the hair originates form a human or an animal. Also, how a human hair retrieved at a crime scene compares with a particular individual is determined.

21. 11-21 ©2011, 2008 Pearson Education, Inc. Upper Saddle River, NJ 07458 FORENSIC SCIENCE: An Introduction, 2 nd ed. By Richard Saferstein Comparing Strands Hair grows at a rate of 1 cm / month –Estimate time passed since cut/color Dyed or colored hair is usually colored throughout the cortex Bleaching completely removes pigment from hair and gives it a yellowish tint

22. 11-22 ©2011, 2008 Pearson Education, Inc. Upper Saddle River, NJ 07458 FORENSIC SCIENCE: An Introduction, 2 nd ed. By Richard Saferstein Comparing Strands In comparing hairs, important features to examine include Matching color, length and diameter of hairs. Presence (or absence) of a medulla Distribution, shape and color intensity of pigment granules present in cortex

23. 11-23 ©2011, 2008 Pearson Education, Inc. Upper Saddle River, NJ 07458 FORENSIC SCIENCE: An Introduction, 2 nd ed. By Richard Saferstein Questions Can the body area from which a hair originated be determined? It is usually easy to determine body area: Head hairs have a smaller diameter and more evenly colored Leg/trunk hair contain more medulla and less uniform distribution of pigment Pubic hairs are short & curly with a continuous medulla Facial hairs are coarse, triangular in cross- section and have blunt tips

24. 11-24 ©2011, 2008 Pearson Education, Inc. Upper Saddle River, NJ 07458 FORENSIC SCIENCE: An Introduction, 2 nd ed. By Richard Saferstein Questions Can the racial origin of hair be determined? In many instances – especially Caucasian or Negroid – but with only with experience Negroid hairs –normally kinky, containing dense, unevenly distributed pigments –cross-section is flat to oval Caucasian hairs –straight or wavy with fine to coarse pigments that are fairly evenly distributed –cross-section is oval to round

25. 11-25 ©2011, 2008 Pearson Education, Inc. Upper Saddle River, NJ 07458 FORENSIC SCIENCE: An Introduction, 2 nd ed. By Richard Saferstein Questions Can the age and sex of an individual be determined from a hair sample? Not with any degree of certainty, EXCEPT Infant hairs are fine and short and have fine pigmentation Presence of dye or bleach may offer some clue to sex Recovery of nuclear DNA from tissue or root would allow determination of sex

26. 11-26 ©2011, 2008 Pearson Education, Inc. Upper Saddle River, NJ 07458 FORENSIC SCIENCE: An Introduction, 2 nd ed. By Richard Saferstein Questions Is it possible to determine if a hair was forcibly removed from the body? Possibly Hair roots with follicular tags indicate hair was pulled out by a person or brushing/combing Absence of follicular tissue does not necessarily mean it wasn’t pulled out –Hairs pulled quickly are much more likely to have follicular tissue than those removed slowly

27. 11-27 ©2011, 2008 Pearson Education, Inc. Upper Saddle River, NJ 07458 FORENSIC SCIENCE: An Introduction, 2 nd ed. By Richard Saferstein Questions Are efforts being made to individualize human hair? Yes Hairs with nuclear DNA from follicular tissue Nuclear DNA from hair roots in anagen phase or entering catagen phase Mitochondrial DNA can be collected from hair shafts 1-2 cm in length –More copies found outside the nucleus –Only mother’s DNA

28. 11-28 ©2011, 2008 Pearson Education, Inc. Upper Saddle River, NJ 07458 FORENSIC SCIENCE: An Introduction, 2 nd ed. By Richard Saferstein Questions Can DNA individualize a human hair? Yes Nuclear DNA produces frequencies of occurrence as low as one in billions or trillions Mitochondrial DNA cannot distinguish between different individuals who are maternally related As a rule, all positive microscopic hair comparisons must be confirmed by DNA analysis.

29. 11-29 ©2011, 2008 Pearson Education, Inc. Upper Saddle River, NJ 07458 FORENSIC SCIENCE: An Introduction, 2 nd ed. By Richard Saferstein Collection and Preservation Questioned hairs submitted to a forensic laboratory must be accompanied by standard or reference samples From the victim of crime and individuals suspected of having deposited hair at the crime scene Must come from the same area of the body

30. 11-30 ©2011, 2008 Pearson Education, Inc. Upper Saddle River, NJ 07458 FORENSIC SCIENCE: An Introduction, 2 nd ed. By Richard Saferstein Collection and Preservation As a general rule, forensic hair comparisons involve either head hair or pubic hair. –The collection of 50 full-length hairs from all areas of the scalp will normally ensure a representative sampling of head hair. –A minimum collection of two dozen full-length pubic hairs should cover the range of characteristics present in pubic hair.

31. 11-31 ©2011, 2008 Pearson Education, Inc. Upper Saddle River, NJ 07458 FORENSIC SCIENCE: An Introduction, 2 nd ed. By Richard Saferstein Collection and Preservation Hair samples are also collected from the victim of suspicious deaths during an autopsy.

32. 11-32 ©2011, 2008 Pearson Education, Inc. Upper Saddle River, NJ 07458 FORENSIC SCIENCE: An Introduction, 2 nd ed. By Richard Saferstein Types of Fibers Fibers are classified into two broad groups Natural Manufactured

33. 11-33 ©2011, 2008 Pearson Education, Inc. Upper Saddle River, NJ 07458 FORENSIC SCIENCE: An Introduction, 2 nd ed. By Richard Saferstein Types of Fibers Natural fibers are derived in whole from animal or plant sources. Plant sources –Cotton Wide use makes its evidential value almost meaningless Ribbon-like shape with twists at irregular intervals –Linen Flax plant

34. 11-34 ©2011, 2008 Pearson Education, Inc. Upper Saddle River, NJ 07458 FORENSIC SCIENCE: An Introduction, 2 nd ed. By Richard Saferstein Types of Fibers Natural fibers are derived in whole from animal or plant sources. Animal sources –Wool (sheep) –Mohair (goat) –Cashmere (goat) –Silk (silk moth cocoons) –Furs Forensic examination uses the same procedure as for animal hair

35. 11-35 ©2011, 2008 Pearson Education, Inc. Upper Saddle River, NJ 07458 FORENSIC SCIENCE: An Introduction, 2 nd ed. By Richard Saferstein Types of Fibers Man-made fibers are manufactured. –Regenerated fibers are manufactured from natural raw materials and include rayon, acetate, and triacetate. –Synthetic fibers are produced solely from synthetic chemicals and include nylons, polyesters, and acrylics.

36. 11-36 ©2011, 2008 Pearson Education, Inc. Upper Saddle River, NJ 07458 FORENSIC SCIENCE: An Introduction, 2 nd ed. By Richard Saferstein Types of Fibers Synthetic fibers were created when scientists developed a method of synthesizing long- chained molecules called polymers.

37. 11-37 ©2011, 2008 Pearson Education, Inc. Upper Saddle River, NJ 07458 FORENSIC SCIENCE: An Introduction, 2 nd ed. By Richard Saferstein Types of Fibers Polymers are composed of a large number of atoms arranged in repeating units known as monomers.

38. 11-38 ©2011, 2008 Pearson Education, Inc. Upper Saddle River, NJ 07458 FORENSIC SCIENCE: An Introduction, 2 nd ed. By Richard Saferstein Fiber Evidence Naturally occurring polymers haven’t been able to be copied yet –Animal hair – chains of amino acids –Cellulose and starch – chains of carbohydrates Synthetic fibers are an extension of chemical principles that nature has used to produce hair and vegetable fibers.

39. 11-39 ©2011, 2008 Pearson Education, Inc. Upper Saddle River, NJ 07458 FORENSIC SCIENCE: An Introduction, 2 nd ed. By Richard Saferstein Fiber Evidence The quality of the fiber evidence depends on the ability of the criminalist to identify the origin of the fiber or at least be able to narrow the possibilities to a limited number of sources. Obviously, if the examiner is presented with fabrics that can be exactly fitted together at their torn edges, it is a virtual certainty that the fabrics were of common origin.

40. 11-40 ©2011, 2008 Pearson Education, Inc. Upper Saddle River, NJ 07458 FORENSIC SCIENCE: An Introduction, 2 nd ed. By Richard Saferstein Fiber Evidence Microscopic comparisons between questioned and standard/reference fibers are initially undertaken for color and diameter characteristics, using a comparison microscope. Other morphological features that could be important in comparing fibers are: –Lengthwise striations on the surface of the fiber. –The presence of delustering particles that reduce shine. – The cross-sectional shape of the fiber.

41. 11-41 ©2011, 2008 Pearson Education, Inc. Upper Saddle River, NJ 07458 FORENSIC SCIENCE: An Introduction, 2 nd ed. By Richard Saferstein Fiber Evidence Wayne Williams was charged and tried for the murder of two individuals in the Atlanta, Georgia region in the early 1980s. Unusual fibers on the victims linked them to a carpet in the Williams home and was a key element in proving Williams’ guilt.

42. 11-42 ©2011, 2008 Pearson Education, Inc. Upper Saddle River, NJ 07458 FORENSIC SCIENCE: An Introduction, 2 nd ed. By Richard Saferstein Fiber Evidence Although two fibers may seem to have the same color when viewed under the microscope, compositional differences may exist in the dyes that were applied to the fibers during the manufacturing process. If two fibers have the same dye composition, probability of coming from same source increases

43. 11-43 ©2011, 2008 Pearson Education, Inc. Upper Saddle River, NJ 07458 FORENSIC SCIENCE: An Introduction, 2 nd ed. By Richard Saferstein Methods for Fiber Comparison The visible light microspectrophotometer is a convenient way for analysts to compare the colors of fibers through spectral patterns. A more detailed analysis of the fiber’s dye composition can be obtained through a chromatographic separation.

44. 11-44 ©2011, 2008 Pearson Education, Inc. Upper Saddle River, NJ 07458 FORENSIC SCIENCE: An Introduction, 2 nd ed. By Richard Saferstein Methods for Fiber Comparison Forensic scientist must choose a test that will yield the most information with the least amount of material. –May only amount to a minute strand recovered from a fingernail scraping

45. 11-45 ©2011, 2008 Pearson Education, Inc. Upper Saddle River, NJ 07458 FORENSIC SCIENCE: An Introduction, 2 nd ed. By Richard Saferstein Methods for Fiber Comparison The generic class of fiber may be determined by Infrared spectrophotometry –a rapid, reliable Polarizing microscope –each polarized plane of light will have a characteristic index of refraction.

46. 11-46 ©2011, 2008 Pearson Education, Inc. Upper Saddle River, NJ 07458 FORENSIC SCIENCE: An Introduction, 2 nd ed. By Richard Saferstein Collection and Preservation The investigator’s task of looking for minute strands of fibers often becomes one of identifying and preserving potential “carriers” of fiber evidence. Relevant articles of clothing should be packaged carefully in separate paper bags. If it is necessary to remove a fiber from an object, the investigator must use clean forceps, place it in a small sheet of paper, fold and label the paper, and place the paper packet inside another container.