Hair • Notes on hair morphology, identification and comparison of hair and collection and preservation of hair evidence

Morphology of hair • Can not individualize hair based on morphology • Hair provides strong corroborative evidence for placing an individual at a crime scene • Hair is an appendage growing out of a hair follicle • Root bulb in follicle>shaft>terminates at tip end • Shaft composed of three layers- cuticle, cortex and medulla

Types of hair follicles

Hair structure • Hair cross section

Cortex, cuticle, medulla

Cuticle • Two features hair good for establishing individual identity; resistance to chemical decomposition and ability retain structural features over a long period of time • Cuticle formed by overlapping cells that point toward tip end each hair • Scales formed by specialized cells hardened and flattened from follicle • It is like the outer paint part of the pencil

Comedy break

Cuticle continued Animal scales appear as shingles on roof

Methods to view scale pattern • Use of a scanning electron microscope • Taking a cast of its surface by embedding it in soft medium like nail polish or softened vinyl and examined by a compound microscope

Cortex • Contained with in cuticle is cortex • It is like the outside wood of surrounding the lead inside a pencil • Major forensic importance embedded with pigment granules that impart hair w/color • Color, shape, distribution of granules important points of comparison among hairs of different individuals

Medulla • Hair cross section continued

Medulla • Collection of cells having the appearance of a central canal running through a hair

Medulla continued • Animals often have medulla occupying more than half the hair’s diameter • This is like the lead on the inside of the pencil • Medullary index measures the diameter of medulla relative to the diameter of the hair shaft & is normally expressed as a fraction • Humans value less than 1/3; most animals one-half or greater

Medulla continued • Presence or appearance of medulla varies from individual to individual & even hairs of the same individual • Not all hairs have medullae & when they do exist the degrees a medullation vary • Humans exhibit no medullae or fragmented ones; rare to have continuous medullation; exceptions Mongoloid race • Animals medullae continuous or interrupted

Medulla types

Comedy break

Medulla continued • Shape of medulla; humans & some animals medullae give a cylindrical appearance • Other animals exhibit patterned shape see figure 8-4 and 8-5 for examples in book • Medulla of a cat looks like a set of pearls

Root • Root and surrounding cells aid in producing hair & continuous growth • Human head hair 3 developmental stages • Shape and size of hair root determine by growth phase • Three phases; anagen, catagen, telogen • Anagen phase up to six years; root attached to follicle continued growth; flame-shaped appearance

Root continued • Follicular tag (translucent piece of tissue surrounding hair shaft near root) is important for individualization of hair; DNA • Catagen phase 2-3 weeks slowing hair growth; roots elongated appearance root bulb shrinks in size/pushed out follicle • Telogen phase starts hair growth ends and root club shaped appearance

Root stages

Identification and comparison of hair • Primary purpose to determine if hair is human or animal • Determine whether human hair retrieved at crime scene compares to hair known from individual • Scale structure, medullary index, medullary shape • Most common request is determine whether or not hair recovered at crime scene compares with hair from suspect

Comedy break

Identification and comparison of hair continued • Comparison microscopes aid in comparing questioned/known samples side by side • Comparing hair; color, length, diameter what is looked at • Presence or absence of a medulla, distribution, shape, color intensity of pigment granules present in cortex • Distinguish dyed or bleached hair

Identification and comparison of hair continued

Identification and comparison of hair continued • Dyed color will often be present in cuticle as well as throughout cortex • Bleaching removes pigment give a yellowish tint • Natural end of hair distinct from dyed hair • Hair grows a centimeter/month so estimating time of dyeing or bleaching can be made

Identification and comparison of hair continued • Morphological abnormalities may be observed for identification purposes • Fungal and nit infections serve link hair specimen to individual • Microscopic hair comparisons must be regarded as presumptive in nature • All positive comparisons confirmed by DNA determination

Ascertaining the present status of hair examination • No, little difficulty is experienced in ascertaining body area • Hair from different areas of the body have unique structures and morphology • Yes, a person can ascertain hair from race; caution and experience should be taken • Age cannot be determined from hair examination except infant hair • Recovery of DNA from root structure determine sex

Ascertaining the present status of hair examination • Examination of hair root can determine if hair fallen out or pulled out of skin

Ascertaining the present status of forensic hair examinations • Hair root with follicular tissue adhering to it, hair pulled out by person by brushing or combing • Bulbous-shaped root free of adhering tissue hair naturally falling out • Absence sheath cells not always relied on • How quickly hair pulled a consideration; sheath cells on quickly pulled hair VS very little if any hairs pulled slowly from scalp

Ascertaining present status forensic hair examinations • Forensic hair examiners link human hair to individual through nuclear DNA • Follicular tag (translucent piece of tissue surrounding hair’s shaft near root) is richest source of DNA associated with hair • Root hair substituted for follicular tag tissue

Ascertaining present status forensic hair examination • Examiners higher rate of extracting DNA from roots in anagen phase or anagen hairs entering catagen phase • If nuclear DNA (both parents to child) isn’t found then mitochondrial DNA can be used • DNA outside of nucleus and transferred only from mother to child

Comedy break

Ascertaining present status forensic hair examination • DNA can individualize a human hair • Nuclear DNA produce frequency of occurrences as low as 1 in billions or trillions • Mitochondrial DNA will not individualize human hair but can exclude a significant portion of population as hair contributors • Mitochondrial DNA cannot distinguish microscopically similar hairs from different individuals who are maternally related

Collection and preservation of hair evidence • Have questioned and standard/reference hairs come from same area of body and adequate number of hair samples of each • Forensic hair comparisons involve either head hair or pubic hair • Collection of 50 full-length hairs from all areas of the scalp • Minimum of 24 full-length hairs from pubic area

Collection and preservation of hair evidence continued • Entire hair length collected because of variance in morphological characteristics like color • Pull hair out of skin or clipping at skin line • Hair samples collected from victim(s) suspicious death during autopsy