Presentation on theme: "Hair 1.Human hair is one of the most frequently found pieces of evidence at the scene of a violent crime. 2.It can provide a link between the criminal."— Presentation transcript:
Hair 1.Human hair is one of the most frequently found pieces of evidence at the scene of a violent crime. 2.It can provide a link between the criminal and the crime. 3.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
Hair Shaft Composed of: Cuticle—outside covering, made of overlapping scales Cortex—inner layer made of keratin and embedded with pigment; also contains air sacs called cortical fusi Medulla—inside layer running down the center of the cortex
The Cuticle 1.The cuticle is the outermost layer of hair which is covered with scales. 2.The scales point toward the tip of the hair. 3.Scales differ among species of animals and are named based on their appearance. 4.The three basic patterns are: –Coronal –Spinous –Imbricate
Variations in the Cuticle 1.Imbricate Cuticle: Indicates that hair sample is human. 2.Spinous Cuticle: Indicates hair sample is from a cat. 3.Coronal Cuticle: Found in dogs, bats and small rodents.
Human Scales In order to visualize the scales: 1.Paint clear fingernail polish on a glass slide. 2.When the polish begins to dry, place a hair on the polish. 3.When it is almost dry, lift off the hair and observe the scale imprints. What pattern is seen in this slide?
The Cortex 1.The cortex gives the hair its shape. 2.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
Two Main Human Pigments 1.Pheomelanin- Found in Blond and Red hair 2.Eumelanin - Found in black and brown hair
The Medulla 1.The medulla is the hair core that is not always visible. The medulla comes in different types and patterns. 2.Types: - Intermittent or interrupted - Fragmented - Continuous - Stacked - Absent—not present
3. Central/middle part of the hair shaft. 4. Shows great variation among people and species.
Human Medulla Human medulla may be continuous, fragmented, or absent.
Medullary Index 1.Determined by measuring the diameter of the medulla and dividing it by the diameter of the hair. 2.Medullary index for human hair is generally less than 1/3. 3.For animal hair, it is usually greater than 1/2.
Different Patterns of Medulla 1.Uniserial 2.Mutiserial 3.Vacuolated 4.Lattice 5.Fragmented amorphous 6.Continuous amorphous 7.Hair may or may not have a medulla.
Hair Shape Can be straight, curly, or kinky, depending on the cross section, which may be round, oval, or crescent-shaped. Round (Straight) Oval (Curly) Crescent moon (Kinky)
Hair Growth 1. Grows about 0.4 mm per day, or 1 cm per month; approximately one-half inch per month 2. Terminology - Anagen—hair is actively growing; lasts up to 5 years - Catagen—hair is not growing; a resting phase - Telogen—follicle is getting ready to push the hair out; lasts two to six months
The Root 1.Human roots look different based on whether they have been forcibly removed or they are telogen hairs and have fallen out. 2.Animal roots vary, but in general have a spear shape. Fallen out Forcibly removed
Racial Origin of Hair 1.Negroid Hair Hair shaft and cuticle Irregular in diameter. Dense, unevenly distributed pigment Opaque hair shaft Cross-sections = flat to oval Negroid or African hair
Racial Origin of Hair (continued) 2.Asian Hair Densely distributed pigments; arranged in large patchy areas or streaks. Medulla: prominent (often broad and continuous) Cuticle: thick Cross-sectional shape: round Mongoloid or Asian hair
Racial Origin of Hair (continued) 3.Caucasian Hair Straight or wavy Sparse to dense pigments Fine to coarse evenly distributed pigments Cross-sections = oval (more oval more wavy)
How can we determine where a hair came from? 1.Scalp hairs – uniform distribution of color and diameter 2.Pubic hairs – Short, curly, wide variations
Variations in hair root 1.Rounded root (no follicle): Indicates the hair fell out naturally. 2. Follicle attached root: Hair was forcibly removed.
Hair Comparison 1.Color 2.Length 3.Diameter 4.Distribution, shape, and color intensity of pigment granules 5.Dyed hair has color in cuticle and cortex 6.Bleaching removes pigment and gives a yellow tint 7.Scale types 8.Presence or absence of medulla 9.Medullary type 10.Medullary pattern 11.Medullary index
DNA from Hair 1.The root contains nuclear DNA. 2.If the hair has been forcibly removed, some follicular tissue containing DNA may be attached. 3.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 more costly than using nuclear DNA.
Collection of Hair 1.Questioned hairs must be accompanied by an adequate number of control samples. From victim From possible suspects From others who may have deposited hair at the scene 2.Control Sample 50 full-length hairs from all areas of scalp 24 full-length pubic hairs
Hair Toxicology 1.Collections must be taken from different locations on the body to get an accurate timeline. 2.Advantages: Easy to collect and store Is externally available Can provide information on the individual’s history of drug use or evidence of poisoning
Identification and Collection of Hair Evidence Collection of visually observed hairs 1.By hand or with tweezers. (Tweezers are NOT recommended they damage the structure of the hair and crush the root (DNA)) 2.Clear tape - Lifts visible and non-visible hair
Identification and Collection of Hair Evidence (Continued) 3.Vacuums - Used on objects that cannot be transported 4.Brushing, scraping or shaking of garment 5.Combing and clipping - Pulls off loose hairs
Comparison of Collected Hair 1.Approximately hairs from various parts of the body should be collected and analyzed 2.Investigators make sure to label the hairs origin and method of collection
Hair as a Chemical Indicator 1.Hair can collect materials that come into the body and are delivered by the blood to the hair root, where they are deposited in the cortex. 2.Many drugs and their metabolites, vitamins, and poisons can now be detected in a few mm of hair. 3.Since hair grows at 1 cm/month, drug use can be traced over a longer period of time.
4.Napoleon died in exile in 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 killed him.