Trace Evidence Hair and Fibers

1. Trace Evidence Hair and Fibers

2. Trace Evidence • Any very small physical material that can be transferred from person to person or to the crime scene. • Includes hair, fibers, glass chips, paint, dirt, dust, and plant materials. • Creates links between suspects, places, and objects because it grabs and clings to clothing, hides in shoe seams, nestles in hair, settles in nooks and crannies, and survives for years. • Most often is the only evidence that connects the suspect with the crime scene. • (Remember Locard’s Principle)

3. Importance of Trace Evidence • Physical Evidence cannot by itself provide for a positive identification of a suspect. • However, lab examination may narrow the origin of such evidence to a group that includes the suspect.

4. 1891 - Han Gross published the first description of the uses of physical evidence to help solve crimes 1897 - Rudolph Virchow became the first person to do an in depth study of hair. 1906 - Hugo Marx wrote a paper on the use of hair in forensic investigations to determine identity. 1916 - Albert Schneider became the first to collect physical evidence with a vacuum. 1920 - Locard becomes known for the exchange principle – the fact that “every contact leaves a trace.” 1931 - Dr. Paul Kirk works on new ways to improve the use of hair in forensic investigations. History Edmond Locard (1877-1966), noted for his exchange principle.

5. Hair Anatomy • Appendage of the skin that grows out of the hair follicle • Three segments: • Root – Shaft – Tip • Shaft is composed of 3 layers: • Cuticle • Cortex • Medulla • Compared to a pencil – Lead is medulla, wood would be the cortex, and the yellow paint the cuticle. • These layers are subjected to the most intense examination.

6. The Root • Provides tools necessary to produce hair and continue hair growth. • If found attached to the hair this suggests the hair was forcibly removed. • DNA analysis can be taken from this area.

7. The Cuticle • The outside covering of hair • Like scales of a fish – always point up • Gives hair stability and a strong resistance to chemical decomposition. • Scale patterns may be viewed by an electron microscope or a cast of the hair’s surface may be made and studied.

8. Cuticle Scale Patterns • Scale patterns can be used for species identification: • Coronal (crown-like)– give the hair a mosaic surface appearance/rare for humans, common for rodents. • Spinous (petal-like)– somewhat triangular, not found in humans but typical in cats , seals, and minks. • Imbricate (flattened)– found in humans and other animals.

9. The Cortex • Part of the hair contained within the cuticle. • Largest portion of the shaft. • Contains hair pigment (color), shapes, and distribution patterns. • Air pocket patterns helps determine race and matches to sources.

10. The Medulla • Appearance of a canal running through a hair. • Can be used to identify the type of species • Medullary Index – measures the diameter of the medulla relative to the diameter of the hair shaft. • Human medullary Index < 0.3 • Most other animals medullary index is 0.5 or greater. • Appearance may differ from individual to individual and even between different hairs of the same individual.

11. Medulla Continued… • May be classified as continuous, interrupted or fragmented, or absent.

12. Medulla Continued… • Shape of the medulla may also vary from species to species. • Ex: Mongoloid race is the only humans to have continuous medullae. • Microspectrophotometry can determine if hair is dyed and how long ago it was colored…. Remember hair is a timeline. Caucasian Mongoloid/Asian African American

13. Identification and Comparison of Hair • Primary purpose of hair examination in a criminal case: • To establish whether the hair is human or animal in origin • To determine whether human hair retrieved at a crime scene matches that of a particular individual. • Features important in hair identification: • Scale structure • Medullary Index • Medullary shape

14. Comparison of Hair Continued… • Examiner must have access to a comprehensive collection of reference standards and the accumulated experience of hundreds of prior hair examinations. • Hair is class evidence • It is not possible, except in rare instances to determine that a hair sample came from a particular individual to the exclusion of all others.

15. However… • Hair when accompanied by a thorough collection of control specimens can be highly distinctive evidence for personal identification. • Determination of where on the body the hair came from will help for better certainty in identification.

16. Forensic Analysis of the Hairs • Head hairs have a soft texture, cut or split tips, and moderate shaft diameter. • Pubic hairs have a course, wiry texture, tapered, rounded, or abraded tips, and a buckling shaft. • Facial hairs have a triangular cross-section and a course in texture. • Eyelash/Eyebrow hairs are saber-like in appearance, short, and stubby. • Limb hairs are soft, and arc-like in appearance. Tips are rounded and abraded; scales rounded due to wear. Head Hair Pubic Hair Beard Hair

17. Things to consider when viewing hair • Length: Length is considered, although hairs may have been cut between the time of deposition of the questioned specimen and the collection of a known sample. In addition, there may be a significant difference in the lengths of the shortest and longest hairs on an individual's head. Tip: The tip can be cut, broken, split, abraded (rounded), or finely pointed as illustrated by An individual's grooming, hygiene, health, and nutrition can affect these features.

18. Dyed hairs possess an unnatural cast or color. In addition, the cuticle will take on the color of the dye

19. Scissor Cut • Razor Cut • Broken Hair • Burned Hair

20. The Statistics… • According to the Royal Canadian Mounted Police: • If a crime scene hair matches a suspects head hair in all respects mentioned (Color, width, distribution and pattern of the medulla, color and distribution pattern of the pigment in the cortex, and the cuticle pattern) the probability that the hair came from someone else is 4,500:1 • Pubic hair drops to 800:1

21. Matching a Culprit to a Lock of Hair • In many instance the examiner can distinguish hair originating from members of different races

22. African AmericanHairs • Curly. • Dense pigment distributed unevenly. • Variations in the diameter of the shaft. • Fragmented or absent medullae. • The cross-section is flattened. Cross Section of a African American Hair Photomicrograph of an AA Head Hair

23. AsianHairs • Coarse and straight shaft, with little diameter variation. • Dense pigment distributed unevenly. • Presence of a continuous medulla. • The cross-section is round. Cross Section of an Asian Hair Photomicrograph of an Asian Head Hair

24. Caucasian Hairs • Straight to wavy. • Fairly evenly distributed, fine pigment. • Moderate shaft diameter, with little variation. • The cross-section is oval. Cross Section of Caucasian Hair Photomicrograph of a Caucasian Hair

25. Other Information about Hair… • Age of a person CAN NOT be determined unless it is from an infant. • Infant hair is fine, short in length, and has fine pigment • Gender CAN NOT be determined. • Chemicals the person may have consumed can be detected. • No two people will have the exact same chemicals in their hair. • Sometimes mitochondrial DNA from the hair shaft can be extracted and compared to the patterns of suspects siblings.

26. Comparison of Animal and Human Hair Humans Animals Medullary Index ≥1/2 Medulla is present for all animals Medulla is continuous for most animals Medulla is patterned for most animals Medullary Index <1/3 Medulla is absent for most humans Medulla is continuous for Mongoloid race Medulla is fragmented – only some animals and humans Medulla is cylindrical in shape (most animals)

27. Collection of Hair Evidence • Must be accompanied by an adequate # of control samples from the victim and the individual suspects. • Hairs from different parts of the body vary significantly in their physical characteristics, so controlled hairs need to come from the same part of the body. • A collection of 50 full- length hairs from all areas of the scalp will ensure a representative sampling of head hair. • A minimum collection of two-dozen (24)full-length pubic hairs should cover the range of characteristics of this type of hair.

28. Collection of Hair Evidence • The search for and collection of hair evidence should begin as soon as possible. Hair evidence is easily transferred to and from the crime scene. • Collection should be done by hand if the location of the hair is important, which is usually the case. Sticky tape and lint rollers may be used to assist. • A special filtered vacuum cleaner may be used to collect hairs and fibers en masse from carpet, bedding, etc. • If the evidence is stuck to another object, the entire object should be packaged and labeled. Evidence Collecting Vacuum Evidence Collecting Kit

29. Collection of Hair Evidence • Once collected, the hair evidence should be packaged into paper packets. • If sticky tape or a lint roller are used, the entire surface used should be packed into a polyethylene storage bag – easy to see through, but with no direct contact. • Control samples need to be collected from the victim, suspect, and other individuals who could have left evidence at the scene. Take from all pertinent regions of the body; 50 head hairs, 24 pubic hairs. Root still in tact is preferable. Evidence Collection Bags Evidence Collecting Lint Roller

30. Forensic Analysis of Hairnalysis of the Hairs • Using a microscope (SEM), forensic scientists can typically determine the species, race, and somatic origin of a hair. They may use comparative microscopy to do one of the following: • Link the suspect to a crime scene, meaning that a control hair matches the evidential hair. • Exclude the suspect from a crime scene, meaning that a control hair does not match the evidential hair. • In addition to comparing hairs in with a microscope, the scientists may test for DNA on the follicular tag, and run a number of tests for drugs and environmental toxins, which will be described at length. Scanning Electron Microscope, a typical device used to study the structures of hair.

31. Forensic Analysis of the Hairs • Hair analysis is used in forensic toxicology to test and determine whether a drug was used. • When a drug is ingested, it enters the blood stream and is broken down to a specific metabolite. • Hair strands normally grow at an average rate of 1.3 centimeters every month; they absorb metabolized drugs that are fed to the hair follicle through the blood stream. • The drug will only disappear if exposure to the drug is ceased, and the hair containing the drug is cut. • Hair analysis can be used for the detection of many therapeutic drugs and recreational drugs, including cocaine, heroin, benzodiazepines (Valium-type drugs) and amphetamines. Depicting how drugs enter the hair. General structure for amphetamines.

32. Fibers • Important evidence in incidents that involve personal contact, such as homicide, assault, or sexual offenses. • Cross-transfers may occur between the clothing of the suspect and the victim, hit and run victim and a vehicle, or fibers may be fixed to screens or glass broken in a breaking-and-entering attempt.

33. Fiber Sources • Examples: This list is NOT all inclusive • Clothing • Carpeting • Car mats • Bedding • Towels • Collection from the suspect or victim must be in a timely manner. • After 4 hours 80% may be gone • After 24 hours 95% may be gone.

34. Classification of Fibers • Natural • Various animals- sheep-wool, goats-mohair and cashmere, camels, llamas, alpacas and vicunas, minks, rabbits, beavers, etc..) • Plants - Cotton, hemp, flax, jute • Minerals – asbestos is woven into materials • Manufactured • Raw cotton or wood pulp is dissolved, cellulose is extracted, and then regenerated into fibers – rayon or acetate. • Synthetic • Fibers that come from polymers – long chains of molecules – nylon and polyester.

35. Identification and Comparison of Fibers • Torn edges may be matched for common origin • Look at color, shape, and diameter of fibers • Lengthwise striations of the surface of the fibers • Pitting of the surface by delustering particles to reduce shine. • Analysis of the fiber’s chemical and dye composition.

36. Some Major Generic Fibers