Hair

1. Hair “For three days after death, hair and fingernails continue to grow but phone calls taper off.” - Johnny Carson Comedian and television host

2. Hair as Evidence • Hair is considered class evidence and is very useful in backing up other circumstantial evidence, such as placing someone at the crime scene. • Human hair is one of the most frequently found pieces of evidence at the scene of a violent crime. It can provide a link between the criminal and the crime (think Locard’s Exchange Principal). • From hair one can determine: • 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 by the person.

3. The Form and Structure of Hair • The average human body has about 5 million hairs. • Most of these are fine down-like hairs that cover practically your entire body. • Hairs are continuously shed and renewed at a rate of about 100 hairs each 24 hour period from the scalp alone. • Hair is made up of complex cross-linked protein called polymers. - These protein polymers are very resistant to breaking down.

4. Morphology of Hair • Hair grows from a tube-like organ in the under layer of the skin (dermis) called a hair follicle. • The hair’s root is embedded into the follicle. • The follicle is linked to the body’s blood supply, so whatever is taken into the body is distributed to the part of the hair that is growing at that time. • The hair’s shaft extends out through the epidermis and ends at a tip.

5. Three Parts to a 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.

6. The Cuticle • Protective coating of the hair that produces a characteristic pattern. • The cuticle is the outermost layer of hair which is covered with scales. - The scales point toward the tip of the hair. - Scales differ between species of animals and are named based on their appearance. • Not useful in individualizing human hair. • Can be used for species identification.

7. There are three basic cuticle patterns: 1. Coronal - example: mouse 2. Spinous - example: cat 3. Imbricate - example: human • In order to visualize human scales: - Paint clear fingernail polish on a glass slide. - When the polish begins to dry, place a hair on the polish. - When almost dry, lift off the hair and observe the scale imprints. .

9. The Cortex • The cortex gives hair its shape. • Made of spindle-shaped cells called keratin that are aligned in a regular array, parallel to the length of the hair. • Embedded with pigment granules that give hair its color. • The color, shape and distribution of the granules provide points for forensic comparison. 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.

10. The Medulla • Canal like structure of cells that runs through the center of the cortex. • The medulla may appear dark or translucent depending on whether there is air, liquid, or pigment within it. • The presence of medulla varies quite a bit: even from hair to hair. • Human head hairs generally have no medulla or may be fragmented (interrupted) ones; except Native Americans and Asians, whose medulla is usually continuous.

12. Forensic Analysis of the Medulla • Intermittent or interrupted • Interrupted • Continuous • Stacked • Absent - not present • Most animals have medulla that is continuous or interrupted. • The shape of the medulla can help identify a species. • Examples: • Most animals and humans: cylindrical • Cats: pearl shape • Deer: spherical occupying whole hair shaft

14. Medullary Index • Determined by measuring the diameter of the medulla and dividing it by the diameter of the hair. • Medullary Index for human hair is generally less than 1/3. • For animal hair, it is usually greater than 1/2.

15. Hair Shape • Hair can be straight, curly or kinky depending on the cross-section, which may be round, oval or crescent-shaped. • It is very risky to assign racial characteristics to hair evidence, but generally: - Hairs found in Asians and Native Americans have a round cross section with no twisting. - Hairs of American and European whites, Mexicans, and people of Middle Eastern descent have an oval cross section, rarely with undulation (twisting), and evenly distributed pigment. - Hairs of people with African heritage have a flat or crescent shaped cross section with twisting, along with clumped pigmentation. Oval (Curly) Crescent moon (Kinky) Round (Straight)

16. Different Types of Human Hair Roots • Human hair grows about 0.5 mm per day or 1 centimeter per month; approximately one half inch per month. • Human hair grows in three developmental stages: - Anagen, catagen, and telogen phases.

17. Anagen Phase • Initial growth phase during which hair follicle is actively producing hair. • Phase may last 5-6 years. • The root is flame like in appearance. • When pulled this root may contain a follicular tag (rich source of DNA). Anagen hair root Root w/ follicular tag

18. Catagen Phase • Hair is not growing; a resting phase. • A transition phase where hair grows at a decreasing rate for two to three weeks. • Shows an elongated appearance as the root bulb shrinks and is being pushed out of hair follicle. Catagen hair root

19. Telogen Phase • Hair growth has ended in this phase. • The root takes on a club-like appearance. • During this two to six month period, the hair will be pushed out of the follicle causing the hair to shed naturally. • Hairs found on a brush or comb tend to be telogen hairs. Telogen hair root

20. Other Hair Facts • Human roots look different based on whether they have been forcibly removed or if they are telogen hairs and have fallen out. • Animal roots will vary, but in general have a spear shape. • The tip of a mature hair will taper to a point. • Cut hair is squared off at the tip. • Frayed hair or split ends results form dryness, lack of conditioner, harsh chemicals, and overuse of a blow dryer. Fallen out Forcibly removed

21. Hair at a Crime Scene • If hairs are collected at a crime scene, the investigator would first determine what species they came from. • Hair is valuable evidence because it does not have a wide range of class characteristics, it is persistent, and it resists degradation. • The more characteristics that are similar between two pieces of hair, the greater the degree of probability of association. • A single difference between the unknown or questioned hair sample and the known or exemplar hair sample, would suggest separate sources.

22. DNA From Hair • The hair root contains nuclear DNA. • If the hair has been forcibly removed, some follicular tissue may be attached containing DNA. • The hair shaft contains abundant mitochondrial DNA, inherited only from the mother. - It can be typed by comparing relatives if no DNA from the body is available. This process is more difficult and costly than using nuclear DNA.

23. Hair Toxicology • Many drugs and their metabolites, vitamins, and poisons can be detected in just a few millimeters of hair. • Drugs are gone from the blood in just a few hours, from the urine in three to five days, but can last years in hair (depending on the length of the hair). • Advantages of using hair to detect drugs: • 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.

24. The Poisoning of Napoleon? • 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.