2. Hair evidence  What information can be gained from analysis of hair?  Hair alone (without follicle cells) is trace evidence & class evidence.  It does not identify a specific individual, but can narrow your suspects down based of certain characteristics of their hair.  Hair is easily left behind at a crime scene.  Adheres easily to carpet, clothes, and many other surfaces (sheets, blankets, car interior, moist surfaces).  Hair has a tough outer coating and does not decompose easily, so it’s durable.  Hair can be analyzed to determine race, history of drug use, evidence poisoning/toxins, nutritional deficiencies.  Hair analysis can sometimes indicate what water supply a person is using!

3. History of Hair Analysis  1883: Alfred Swaine Taylor and Thomas Stevenson publish The Principles and Practice of Medical Jurisprudence and include a chapter on using hair in forensic investigations.  1910: Victor Balthazar & Marcell Lambert (French forensic scientists) publish Le Poil de l’Homme et des Animaux (the hair of man and animals) which includes microscopic studies of hair from most mammals.  1934: Dr. Sydney Smith uses a comparison microscope to perform side-by-side analysis of hairs collected from a crime scene.  Today hair analysis includes neutron activation analysis (NAA), chemical analysis, and DNA analysis

4. The Function of Hair  Why do mammals (including humans) have hair?

5. The Function of Hair  Helps to regulate body temperature  What happens when you get cold? Why?  Protects the skin against sunlight  Skip the “shave” at the dog groomer in summer  Acts as a sensory organ  When hair is very dense, …it’s called fur.

6. The Structure of Hair  Hair originates from the skin.  Your skin is know as the Integumentary system.  Hair is an “accessory organ” to your skin.  The skin has 3 layers:  Epidermis (most superficial layer, at the surface)  Dermis (middle layer)  Hypodermis (deepest layer)  Hair originates from the hair bulb, is surrounded by the hair follicle, and is located in the dermis.  The end of the follicle is called the papilla, this is where the blood vessels meet the hair to supply nutrients.

7. The Structure of Hair  There is generally a sebaceous gland, aka an oil gland, associated with each hair bulb.  Helps water proof the hair and protect it from drying out.  Also a muscle that attaches to the hair follicle to erect the hair when stimulated (cold or scared).  The hair shaft is what you see (the hair on your arm or on your head).

8. The Structure of Hair  The cuticle of the hair itself is composed of keratin, which is a protein produced in the skin.  Proteins are made up of chains of amino acids that are connected by strong bonds, making hair strong and flexible.  The hair shaft is made up of 3 layers: the medulla, the cortex, and the outer cuticle.  Pencil analogy: -Central medulla -Cortex surrounds medulla -Cuticle on outside

9. The Cuticle  The outer layer of the hair shaft, made up of keratin.  The scales point away from the scalp.  This can indicate where the “younger” part of the hair is (closest to the scalp).  Useful when looking for drugs or toxins at a specific point in time.  Humans have scales that are flattened and narrow, called imbricate scales.  Some animals have hair with different scales, this allows scientists to distinguish human hair from animal hair.  Coronal scales have the appearance of a stack of crowns.  Spinous scales resemble petals.

10. Imbricate - Human Spinous - cats Coronal - rodents

11. The Cortex  Contains most of the pigment granules, called melanin. This gives the hair its color.  Pigment distribution varies from person to person  Some people have larger pigment granules, giving a more uneven distribution when viewed under a microscope.

12. The Medulla  The center of the hair is called the medulla.  There are different patterns that a person could have  Continuous  Interrupted  Fragmented/segmented  Solid  Absent  There is also significant differences between species.

13. Medulla patterns

14. Variation in Hair  Shape: hair may be circular, triangular, flattened, or irregular.  Length  Color: depends on distribution of pigment granules.  Human hair is usually one color along the entire length unless it has been artificially dyed.  Animals often have pigments found in solid masses called ovoid bodies, this is why the color of animal hair can appear banded.  Texture:  Vibrissa – the whiskers of many animals  Bristle – coarse hair that provides a protective coat  Wool – fine hairs that cover the bodies of mammals and protect from wet & cold  Diameter: The ratio of the diameter of the medulla to the diameter of the hair is called the medullary index.  Animals have a greater medullary index than humans.

15. Human Hair  Head and body hair of humans is intermediate combining the characteristics of bristle and wool.  4 types:  Primordial hairs – appears in 3 rd month of gestation  Lanugo hairs – replaces the primordial hairs, appears around the 5 th month of gestation and are generally shed by the 8 th month of gestation.  Vellus hairs – soft hairs spread uniformly all over the body  Terminal hair – found on the scalp, eyebrows/eyelashes, limbs/body, pubic, & axillary regions.

16. Life Cycle of Hair  Hair proceeds through 3 stages as it develops.  Anagen stage: Period of active growth when cells around the follicle are rapidly dividing.  Lasts 2-6 years on the scalp, but may be less on other areas of the body.  Canagen stage: Period of transition, hair follicle shrinks & papilla detaches  Telogen phase: Follicle remains dormant, eventually hair will loosen and fall out and the anagen stage begins again.

17. Hair as evidence  Review Locard’s exchange principle  Whenever 2 objects come in contact, some transfer of material will occur.  Hair is trace evidence  Hair can be collected by plucking, shaking, placing tape over a surface, using a special vacuum.  If a large number of hairs are collected from a crime scene the technician has to compare the hairs from the crime scene to hairs from the victim and/or suspect.

18. Hair analysis  Can be analyzed macroscopically and microscopically.  Macroscopic analyses include length, color, texture, curliness.  Microscopic analyses include medulla pattern, cortex pigmentation, type of scales on the cuticle, and medullary index.  Many dyes will fluoresce under certain types of light.  Chemical tests can be used to determine presence of toxins or drugs.  If hair is forcibly removed the hair follicle may be present.  This is known as a follicular tag.  Blood and tissue attached to the tag may be analyzed for blood type and DNA analysis.

19. Chemical analysis  By testing different parts of the hair it’s possible to establish a timeline for when exposure to poisons or other toxins occurred.  Hair grows about 1.3 cm per month, so for example if a toxin occurs at 9cm from the root, you would divide by 1.3 to get the approximate time that the exposure occurred.  Neutron Activation Analysis (NAA) can be used to identify up to 14 elements in a single 2cm strand of hair.  Including: antimony, argon, bromine, copper, gold, manganese, silver, sodium, arsenic, chlorine, and zinc  The probability of 2 hairs have the same profile is very low.

20. Any questions?