Hair

Learning Objectives Recognize and understand the cuticle, cortex, and medulla areas of hair List the three phases of hair growth Appreciate the distinction between animal and human hairs List hair features that are useful for the microscopic comparison of human hairs Explain the proper collection of forensic hair evidence Describe and understand the role of DNA typing in hair comparisons

Hair Hair is encountered as physical evidence in a wide variety of crimes. Although it is not yet possible to individualize a human hair to any single head or body through its morphology, it still has value as physical evidence. When properly collected and submitted to the laboratory accompanied by an adequate number of standard/reference samples, hair can provide strong corroborative evidence for placing an individual at a crime scene.

HAIR Hair is an appendage of the skin that grows out of an organ known as the hair follicle. The length of a hair extends from its root or bulb embedded in the follicle, continues into a shaft, and terminates at a tip end. It is the shaft, which is composed of three layers—the cuticle, cortex, and medulla—that is subjected to the most intense examination by the forensic scientist. FYI: There are about 100,000 scalp hairs on the average person

Analogy: Hair is Like a Pencil How is the morphology of a hair like that of a pencil? Eraser is the Root Paint is the Cuticle Wood is the Cortex Lead is the Medulla

Cuticle Cuticle: the scale structure covering the exterior of the hair. The scales always point towards the tip of the hair. The scale pattern is useful in species identification.

Cuticle Scales of most animal hair are like shingles on a roof. Variety of patterns are important in species identification. Viewed through scanning electron microscope Make a cast of surface Embed hair in a soft medium (clear nail polish or softened vinyl) and let harden Remove hair and an impression of cuticle will be left behind Ideal for examination under a microscope http://www.telegraph.co.uk/science/picture-galleries/7924099/Creepy-crawlies-Amazing-Scanning-Electron-Microscope-pictures-of-insects-and-spiders.html

Coronal Cuticle

Imbricate Cuticle

Spinous Cuticle

Dog Hair Human Pubic Hair Deer Hair Cat Hair Mouse Hair

Cortex Cortex: the main body of the hair shaft Contained within the protective layer of the cuticle. Forensic Importance: embedded with pigment granules that impart hair with color. The color, shape, and distribution of these granules provide the criminalist with important points of comparison among hair of different individuals

Pigment Granules are Absent in Grey Hair ←brown red→ Pigment Granules are Absent in Grey Hair

Medulla Medulla: a cellular column running through the center of the hair. The medullary index measures the diameter of the medulla relative to the diameter of the hair shaft. For humans, the medulla generally occupies less than one-third the diameter of the shaft, while for animals it is generally one-half or greater. The medulla may be continuous, interrupted, fragmented, or absent. The presence of the medulla varies from individual to individual and even among hairs of a given individual. Medullae also have different shapes, depending the species.

Medulla Human head hairs generally have no medulla or have fragmented ones Most animals have medullae that are either continuous or interrupted An interesting feature of the medulla is its shape: Humans and many animals have medullae that give a nearly cylindrical appearance Other animals exhibit medullae that have a patterned shape Cat: string of pearls Deer: spherical cells that occupy entire hair shaft http://phs.psdr3.org/science/forensics/answers/traceans.html

Root Provide the tools necessary to grow hair and continue its growth (along with other surrounding cells contained within the hair follicle) Human head hair grows in three developmental stages and the shape and size of the hair root is determined by the growth phase in which the hair happens to be. Anagen Phase Catagen Phase Telogen Phase

Anagen Phase The initial growth phase during which the hair follicle actively produced hair. May last up to 6 years The root is attached to the follicle for continued growth, giving the root bulb a flame-shaped appearance When pulled from the root, some anagen hairs will have a follicular tag – a translucent piece of tissue surrounding the hair’s shaft near the root; it contains the richest source of DNA associated with hair!

Catagen Phase A transition stage between the anagen and telogen phases of hair growth. Hair continues to grow during this phase, but at a decreasing rate Lasts 2-3 weeks Roots take on an elongated appearance as the root bulb shrinks in size and is being pushed out of the hair follicle

Telogen Phase The final growth phase in which hair naturally falls out of the skin. Once hair growth ends, the telogen phase begins and the root takes on a club-shaped appearance During a 2 to 6 month period the hair is pushed out of the follicle causing the hair to naturally shed FYI: Most people lose about 100 scalp hairs a day

Identification and Comparison of Hair When hair evidence is present in a criminal case the prime purpose for its examination is: To determine if it is human or animal in origin Scale structure, medullary index, and medullary shape are features that are important in hair identification To determine whether human hair retrieved at a crime scene compares with hair from a particular individual In making a hair comparison, a comparison microscope is an invaluable tool Allows the examiner to view both hairs side-by-side Because hair from any part of the body exhibits a range of characteristics, it is necessary to have an adequate number of known hairs

Characteristics of Hair used for Comparison Purposes Color Length Diameter Presence or absence of medulla Distribution, shape, and color intensity of pigment granules present in the cortex Dyed or bleached (from natural) Dyed: color present in cuticle and throughout cortex Bleaching: remove pigment and gives it yellowish tint Grows about 1 cm/month, therefore the time from the last dyeing or bleaching can be estimated Abnormalities due to diseases or deficiencies Presence of fungal and nit infections

Uses of Hair at Crime Scene Vernon J. Gerberth, in Practical Homicide Investigation, points out that hair (and fiber) evidence is useful in: Helping to establish the scope of the crime scene Placing a perpetrator at a scene Connecting a suspect with a weapon Supporting witness statements Connecting crime scene areas (abduction, vehicle used, dump site)

Questions Concerning Hair Examination Can the body area from which a hair originated be determined? Can the racial origin of hair be determined? Can the age and sex of an individual be determined from a hair sample? Is it possible to determine if a hair was forcibly removed from the body? Are efforts being made to individualize human hair? Can DNA individualize a human hair?

Collection of Hair Evidence As a general rule, forensic hair comparisons involve either head hair or pubic hair. Imperative that the questioned and standard/reference hairs come from the same area of the body The collection of 50 full-length hairs from all areas of the scalp will normally ensure a representative sampling of head hair. A minimum collection of two dozen full-length pubic hairs should cover the range of characteristics present in pubic hair. Hair samples are also collected from the victims of suspicious deaths during an autopsy.

Can the Body Area of a Hair be Determined? This task is relatively simple. Scalp Hairs show little diameter variation have a more uniform pigment color Pubic Hairs short and curly wide variation in shaft diameter usually have continuous medullae Beard Hairs coarse triangular cross section blunt tips from cutting and shaving

Can the Age and Sex of a Hair be Determined? Age cannot be learned with any degree of certainty except with infant hairs, which are short, fine, have fine pigment, and are rudimentary in character. The presence of bleaches and dyes may play a role in the determination of gender; however, these characteristics are less valuable than they were in the past Recovering nuclear DNA from tissue adhering to the hair or from the root structure of the hair will allow for determination of gender.

Can the Racial Origin of Hair be Determined? African Head Hair Normally kinky Contains dense, unevenly distributed pigments Cross section is flat to oval Caucasian Head Hair Usually straight or wavy Fine to coarse pigments that are more evenly distributed Cross-section is oval to round All of these observations are general in nature, with many possible exceptions.

Is it Possible to Determine if Hair was Forcibly Removed? Examine Hair Root Pulled Hair: if follicular tissue is present the hair was probably pulled out by another person or by brushing or combing Natural Fall Out: if the root is bulbous-shaped with no adhering follicular tissue

Are Efforts Being Made to Individualize Human Hair? Nuclear DNA DNA present within the nucleus of a cell; this form of DNA is inherited from both parents Forensic hair examiners can link human hair to a particular individual by characterizing the nuclear DNA present in the hair root or the follicular tag With no follicular tag present, the examiner must extract DNA from the hair root Higher rate of success extracting DNA during the anagen phase or from hairs entering the catagen phase (telogen phase hairs have an inadequate mount of DNA to successfully type)

Are Efforts Being Made to Individualize Human Hair? Mitochondrial DNA DNA present in small structures (mitochondria) outside the nucleus of a cell. Mitochondria are responsible for supplying energy to the cell. This form of DNA is maternally inherited. There are many more copies of mitochondrial DNA located in our cells as compared to nuclear DNA The success rate for finding and typing mitochondrial DNA is much greater from hair because it has limited quantities of nuclear DNA As a rule, all positive microscopical hair comparisons must be confirmed by DNA analysis.