Forensic Science Presentation developed by T. Trimpe

Vocabulary Class Evidence Class Evidence- material that connects an individual or thing to a certain group. Individual Evidence Individual Evidence – a kind of evidence that identifies a particular person or thing Trace evidence Trace evidence – small but measurable amounts of physical or biological material found at a crime scene. Comparison Microscope Comparison Microscope – a compound microscope that allows the side-by-side comparison of samples, such as hair or fibers.

Cuticle Cuticle – the tough outer covering of a hair composed of overlapping scales. Hair Follicle Hair Follicle – the actively growing root or base of a hair containing DNA and living cells. Cortex Cortex – the region of a hair located outside of the medulla containing granules of pigment. Medulla Medulla – the central core of a hair fiber. Keratin Keratin – a type of fibrous protein that makes up the majority of the cortex of a hair.

Melanin granules Melanin granules – bits of pigment found in the cortex of a hair. Neutron activation analysis Neutron activation analysis – a method of analysis that determines composition of elements in a sample.

Hair A good indicator of individual identity –Resistant to chemical decomposition –Retains structural features over time –Hair is not an absolute indicator of identity but can be a good indicator of identity

The Anatomy of Hair Hair is generally used as a class characteristic not an individual characteristic: –Individual: can be related to a particular person or thing –Class: can be related to groups of people or things Using hair samples to ID a particular individual is very difficult

Morphology of Hair Three main regions: root, shaft, and tip –Root: The part that was growing in the follicle. This is the widest part of the hair –Shaft: The middle of the length of the hair (from the root to the tip). This is where the hair tapers –Tip: The end of the hair farthest away from the root. The hair is narrowest at the tip

Sources: & Hair is composed of the protein keratin, which is also the primary component of finger and toe nails. Hair is produced from a structure called the hair follicle. Humans develop hair follicles during fetal development, and no new follicles are produced after birth. Hair color is mostly the result of pigments, which are chemical compounds that reflect certain wavelengths of visible light. Biology of Hair

Hair shape (round or oval) and texture (curly or straight) is influenced heavily by genes. The physical appearance of hair can be affected by nutritional status and intentional alteration (heat curling, perms, straightening, etc.). The body area (head, arm, leg, back, etc.) from which a hair originated can be determined by the sample’s length, shape, size, color, and other physical characteristics. In order to test hair evidence for DNA, the root must be present. In order to test hair evidence for DNA, the root must be present. Sources: & Biology of Hair

Hair Structure Hair is composed of three principal parts: The structure of hair has been compared to that of a pencil with the medulla being the lead, the cortex being the wood and the cuticle being the paint on the outside. Cuticle – outer coating composed of overlapping scales Cortex – protein-rich structure around the medulla that contains pigment Medulla – central core (may be absent)

Cortex Largest part of hair shaft Contains most of the pigment granules (melanin) The cortex varies in: Thickness Texture Color Distribution of the cortex is perhaps the most important component in determining from which individual a human hair may have come. Microscopic examination can also reveal the condition and shape of the root and tip. Info: Image: Hair Structure

Characteristics of the cuticle may be important in distinguishing between hairs of different species but are often not useful in distinguishing between different people. Hair Structure Cuticle Transparent outer layer of the hair shaft Covered in scales that point toward the tip Made of scales Human : flat and narrow (imbricate) Animal : different types (coronal, spinous) The cuticle varies in: Its scales, How many there are per centimeter, How much they overlap, Their overall shape, and How much they protrude from the surface Its thickness, and Whether or not it contains pigment. Coronal “Crown Shaped” Scales Imbricate “Flattened” Scales Spinous “Spiny” Scales

Human: Tend to be unorganized and overlap like roof shingles Cuticle Man vs. Beast from

Cuticle Photographs Spinous or petal-like scales are triangular in shape and protrude from the hair shaft. They are found at the proximal region of mink hairs and on the fur hairs of seals, cats, and some other animals. They are never found in human hairs. Photomicrograph of the proximal scale pattern in mink hairs. The imbricate or flattened scales type consists of overlapping scales with narrow margins. They are commonly found in human hairs and many animal hairs.

Medulla— Center of hair (Predominant feature of hair) Can be: Hollow tube or filled with cells: Can be absent Fragmented or segmented Continuous or doubled Pigmented or non-pigmented The medulla may vary in: Thickness Continuity - one continuous structure or broken into pieces Opacity - how much light is able to pass through it Like the cuticle, the medulla can be important for distinguishing between hairs of different species, but often does not lend much important information to the differentiation between hairs from different people. Hair Structure

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Medullae in Human Hair Continuous/Double –No breaks Interrupted –Few short breaks

Medullae in Human Hair cont Fragmented –Few parts of the medullae visible Absent –No medullae visible

Medulla Examples Photomicrograph of Animal Hair with vacuolated medullae. Photomicrograph of Deer Medulla with lattice-shaped medulla. The above examples have a well-defined appearance and came from a rabbit.

Hair Identification Animal Versus Human Hairs Human hairs are distinguishable from hairs of other mammals. Animal hairs are classified into the following three basic types. Guard hairs that form the outer coat of an animal and provide protection Fur or wool hairs that form the inner coat of an animal and provide insulation Tactile hairs (whiskers) that are found on the head of animals provide sensory functions

Hair From Different Parts of the Body Varies from region to region of the same person Six types of hair on the human body –Head hair –Eyebrows and eyelashes –Beard and mustache hair –Underarm hair –Auxiliary or body hair –Pubic hair Each has its own shape and characteristics

Life Cycle The root: provides for growth of old and new hair –Three phases of hair growth: Anagen (up to 6 yrs): root attached to follicle for continued growth; root bulb is flame-shaped Catagen (2-3 weeks): slowed growth; root bulb has an elongated appearance Telogen (2-6 months): hair growth ends (becomes dormant) and is shed; root bulb is club-shaped (10-18% of hair)

Hair Comparison Pigment granules are small, dark, and solid structures that are granular in appearance. They vary in color, size, and distribution in a single hair. In humans, pigment granules are commonly distributed toward the cuticle as shown in Figure 1, except in red-haired individuals as in Figure 2. Animal hairs have the pigment granules commonly distributed toward the medulla, as shown in Figure 3.Figure 1Figure 2Figure 3 Figure 1 Figure 2 Figure 3

Other Factors to Effect Hair Race Appearance Pigment Granules Cross Section OtherPicture European Generally straight or wavy Small and evenly distributed Oval or round of moderate diameter with minimal variation Color may be blond, red, brown, or black Asian StraightDensely distributed Round with large diameter Shaft tends to be coarse and straight Thick cuticle Continuous medulla African Kinky, curly, coiled Densely distributed, clumped, may differ in size and shape Flattened with moderate to small diameter and considerabl e variation

Hair Comparison Highly subjective comparative test DNA analysis of hair is a much more reliable testing technique Nuclear DNA Analysis: –DNA found in the nucleus of the cell »Must have follicular tag or root structure present to test Mitochondrial DNA Analysis: –DNA found in cellular material outside of the nucleus –Can be tested without follicle or root structure –More copies of mitochondrial DNA in cells

Collection and Preservation Of Hair Evidence Must be submitted with an adequate sample of hair from the victim of a crime, those entering a crime scene, or a suspect Hair samples must be obtained from the same parts of the body Usually involve head or pubic hair Hair must be pulled out of the skin or by clipping it at the skin line Hair is collected from the victims of suspicious deaths at autopsy