Human Hair Analysis Hair and Fiber 1 Hair Analysis Encountered in a wide variety of crimes Especially useful in rape cases Also useful in illegal drug usage cases (toxicology) Many attempts have been made to positively identify a suspect but all have failed Hair is usually class characteristic only Typically need more than one Vital Properties Species identification Color/Pigment Length Diameter Internal characteristics Dye/Bleaching Hair as Evidence Hair evidence is evaluated by physical microscopy or chemical analysis Toxicology Hair acts like a time capsule Base of hair shows most recent use Protein structure “freezes” evidence of drugs, heavy metals, etc. in hair Typical human head hair growth is 1 cm per month Rape/Homicide Source of DNA in follicular tissue Hair as Evidence Species identification Most species of mammals are distinctly different from each other under a microscope Human ethnicity Can usually identify ethnicity in humans Human Ethnicity Caucasoid Mongoloid Usually straight or wavy Evenly distributed, usually fine pigmentation Oval to round cross section Fragmented/absent medulla Usually straight Usually even, dense pigmentation Typical human hair cross Continuous medulla (defining characteristic) sections Negroid Kinky Dense, unevenly distributed pigment Flat to oval cross section Fragmented/absent medulla “Buckling” often seen Hair Evidence Myths Age Age can not be determined with any amount of certainty Only infants seem to have distinct characteristics Usually very fine Gender Gender can not be determined without follicle and DNA analysis Male/Female structure identical Differences mainly genetic in nature Hair Evidence Myths DNA extraction Can be extracted from follicular tissue or root (in some cases) Cut hair without the root usually does not contain enough DNA to type If forcefully removed, follicle tissue w/ DNA likely attached to root Hair that falls out naturally does not contain adhering tissue Body Hair Types Forensically valuable hair Scalp hair Little diameter differences Uniform pigment Exposure to environmental conditions make immediate processing vital Pubic hair Vary widely in diameter Usually curly Short length Less exposure to elements allows for collection long after crime Body Hair Types Lesser forensic value Most other body hairs are too variable in appearance to be valuable for forensics Characteristics are in no way linked to patterns found on scalp hair Can be used to determine a suspect’s presence at scene but not often used Three types Limb - arm, leg Fringe hair - neck, sideburns, upper leg, back Axillary - eyebrows, nose, underarm Hair Structure Structural components Epidermis Outermost layer of skin Pitted with hair follicles Root Portion of hair below skin Follicle Only segment of hair that is living Source cells from which hair grows Below skin in the bulb Hair Structure Structural components Arrector (Erector) Muscle Can cause hair to stand on end Also source of “goosebumps” Many animals have control over these muscles Hair Structure Structural components Hair shaft Composed of protein keratin Structurally the same as fingernails Three layers Cuticle, Cortex, Medulla Hair Structure Structural components Cuticle Provides support for hair Non-living Consists of overlapping external scales different than most other mammals Scales very resistant to decomposition Makes for perfect physical evidence Hair Structure Structural components Cortex Inner layer of hair Contain pigment granules Melanin protein Distribution of pigment helps to determine particular individuals Hair Structure Structural components Medulla A “tube” of cells that run up the center of the cortex Width of medulla is vitally important in identifying species Ratio of hair width to medulla width is called medullary index Hair Structure Structural components Medulla Humans have less than 1/3 medulla, most other animals at least ½ Comparison of human hair (left), deer hair (top) and dog hair (right) Hair Structure Structural components Medulla Not always present in certain ethnicities One person can have multiple medulla structures Continuous Interrupted Fragmented Human Medulla Types Typical human medulla types. From left to right: Continuous, Interrupted, Fragmented. Hair Structure Artist’s conception and electron microscope images of a human hair with cuticle, cortex and (to a lesser extent) medulla Hair Growth Growth cycle has three distinct phases Hair can stay on head for approx. 6 years If forcefully pulled out and in one of first two phases, follicle tissue will likely be found with the hair follicle (right) Diagram showing the three phases of hair growth Hair Growth Anagen Up to six years Root attached to follicle Root will have a “flame” shape If pulled out, will usu. have follicular tissue and show evidence of stretching/force Growth originates at base of hair and grows up 80-90% of all hair will be in this phase (Above)Electron microscope image showing new anagen follicles erupting from the epidermis. (Below) A typical anagen follicle with attached tissue. Hair Growth Catagen Two to three weeks Growth slower Root shrinks and is pushed out of follicle Usu. has a shrunken appearance 2% of all hair Transition phase Hair Growth Telogen Two to six months No growth Root has a club shape with no tissue Is shed naturally 10-18% of all hair A typical telogen hair follicle. Note the absence of follicular tissue. Hair Microscopy Damaged cuticle showing loose scales. Typical wear and tear with dislodged scales and other debris on hair follicle. Hair Microscopy Severely damaged hair that may be the result of braiding or forceful removal. A “split end” on a hair follicle. Also note evidence of cutting by sharp scissors. Electric clippers usually leave much more ragged marks. Hair Microscopy A twisted/stretched root…clear indicator of forceful removal. Tight, twisted appearance and scorch marks of hair exposed to high heat. The Atlanta Child Murders 1979-1981, 29 black males were murdered (ages 7-16 except for last 7 who were 17-27) Only common evidence were fibers and presence of dog hair Two artificial fibers ID’ed After info. leaked to press, M.O. changed and bodies were dumped in river PD staked out Chatahoochee River Strangled, beaten, asphyxiated PD heard a loud splash and stopped a suspect (Wayne Williams) Claimed it was garbage Suspect released but body later found nearby w/ single carpet fiber in hair The Atlanta Child Murders Warrant obtained for Williams’ house and found matching carpet and dog hair/fibers Expert assistance obtained from DuPont corporation Exhaustive use of statistical likelihood of particular carpet being found in a single Atlanta home 1:7792 Additional fiber matches w/ victims’ found from Williams’ car Chevrolet assisted in this part of investigation Statistical possibility 1:3828 The Atlanta Child Murders Combined, 1:30 million chance of both matches being achieved In total, 29 fiber type matches found between Williams’ possessions and victims Found guilty after 12 hours of deliberation Serving 2 life sentences Still maintains innocence and has attempted retrials Wayne Williams at his arraignment in February 1982.