Forensics of Hair Analysis

Hair Forensics Helpful in demonstrating physical contact with a suspect Hair is ‘class evidence’ not individual evidence - varies in texture from one region of the body to another Until recently, the comparison microscope was considered the only reliable tool for the identification and comparison of the microscopic characteristics found in hair Today, nuclear and mitochondrial DNA (mtDNA) testing can provide additional information that can influence the value of microscopic examinations

Hair Evidence Standard Students will demonstrate the ability to collect, preserve, and identify evidence found at a crime scene. Objectives 1. Describe the cuticle, cortex, medulla, and root of hair. 2. Explain the distinction between animal and human hairs. 3. List hair features that are useful for the comparison of human hair. 4. Explain the proper collection of hair evidence.

The Biology of Hair An appendage of the skin that grows out of an organ known as the hair follicle. Extends from its root or bulb embedded in the follicle, continues into a shaft, and terminates at a tip end. Hair follicle: sac-like anatomical structure from which hair grows. Sebaceous gland: gland that secretes sebum, which lubricates the skin and hair. Arrector pili muscle: muscle that elevates the hair. Root of hair: part of the hair implanted in the dermis. Papilla: part of the hair connected to the conjunctival tissue. Inner root sheath: sheath formed of several layers of cells. Connective tissue sheath: girdle enclosing the epithelial sheath and connecting to the conjunctival tissue. Epidermis: outer layer of the skin. Hair shaft: a filament that grows from the skin.

DNA Analysis Only possible if ‘bulb’ at the base of the hair is intact

Basic Hair Structure

Part 1 Hair Background Grows from a collection of cells called a follicle The hair shaft is composed of three parts: 1. cuticle – outside covering of hair shaft, can look like overlapping roof shingles

Cortex – inside the cuticle, a pigmented layer Medulla – runs down the center of the hair shaft

Cuticle of Hair Outside covering of hair that resists chemical decomposition. Formed by overlapping scales that point towards the tip end of the hair. Scales are made from hardened/keratinized cells that come from the follicle. Cuticle of a healthy hair. The scales lie flat, and are covered with oil, making the hair feel smooth and look glossy. The scales make the hair stiff, and protect the inside A hair with a damaged cuticle, perhaps from brushing, coloring, or blow-drying. The hair looks dull, and scales flaking off may expose the inner layers, leading to further damage.

Medulla The medulla is a central core of cells that may be present in the hair. Human Animal Deer

Human Medullary Patterns has four types: Continuous medullary canal Also in animals, Mongoloid race Interrupted medulla (regular interruption) Also in animals Fragmented medulla (interruption irregular) Absent

Medulla The medulla, when present in human hairs, is generally less than one-third the overall diameter of the hair shaft. The medulla in animal hairs is normally continuous and structured and generally occupies an area of greater than one-third the overall diameter of the hair shaft. There are many more characteristics of hair that are too numerous to discuss for the purpose of this lab

Cortex – pigment distribution Human hairs are generally consistent in color and pigmentation throughout the length of the hair shaft, whereas animal hairs may exhibit radical color changes in a short distance, called banding. The pigmentation of human hairs is evenly distributed, or slightly more dense toward the cuticle, whereas the pigmentation of animal hairs is more centrally distributed, although more dense toward the medulla.

Hair Forensics Hairs found on a knife or club may support a murder and/or assault weapon claim. A questioned hair specimen can be compared microscopically with hairs from a known individual, side-by-side. Human hairs can be classified by racial origin such as Caucasian (European origin), African-American (African origin), and Mongoloid (Asian origin). In some instances, the racial characteristics exhibited are not clearly defined, indicating the hair may be of mixed-racial origin.

Hair Forensics The region of the body where a hair originated can be determined with considerable accuracy by its gross appearance and microscopic characteristics. The length and color can be determined. It can also be determined whether the hair was forcibly removed, damaged by burning or crushing, or artificially treated by dyeing or bleaching.

Hair Forensics: Collection Hairs can be recovered from items using a number of different techniques. Some of the methods used to collect hairs from clothing and bedding items are scraping, shaking, taping, and picking. Debris from large carpeted surfaces might be vacuumed into a filtered canister. If the specific location of a hair on a clothing item is important, it might be necessary to pick off the hair or tape the item and record where the hair was removed.

Packaging of Hair Evidence Recover all hair present. If possible, use tweezers to pick up hair, place in paper bindles or coin envelopes which should then be folded and sealed in larger envelopes. Label the outer sealed envelope. If hair is attached, such as in dry blood, or caught in metal or a crack of glass, do not attempt to remove it but rather leave hair intact on the object. If the object is small, mark it, wrap it, and seal it in an envelope. If the object is large, wrap the area containing the hair in paper to prevent loss of hairs during shipment

Hair Forensics: Which Hairs? 25-50 randomly selected head hairs are generally considered adequate to represent the range of hair characteristics of that individual. All collected hairs must be full-length so that the investigator can see if the color and morphological features vary throughout the length of the hair. Questioned and Reference hair must come from same area of the body; one cannot, for instance compare head hair to pubic hair.

Things to consider when viewing hair Length: Length is considered, although hairs may have been cut between the time of deposition of the questioned specimen and the collection of a known sample. In addition, there may be a significant difference in the lengths of the shortest and longest hairs on an individual's head. Tip: The tip can be cut, broken, split, abraded (rounded), or finely pointed as illustrated by An individual's grooming, hygiene, health, and nutrition can affect these features.

Additional Information Individuals of Oriental origin usually have a continuous medulla Dyed hair shows color distributed in cortex and medulla Bleached hair has a yellowish tint As hair grows, natural color returns