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Hair

Locard Exchange Principle

Whenever two objects come into contact with one another, there is exchange of materials between them.

Morphology

form and structure

Polymer

A molecule consisting of many identical repeating unit; polymers can be naturally occurring or synthetic

Cuticle

Tough, clear outside covering of the hair shaft

Cortex

Middle layer of the hair shaft that provides strength; comprises most of the hair mass

Medulla

The spongy interior core of hair that gives it flexibility; appears as a canal in the middle of the shaft.

Keratin

A tough protein polymer made up of about 20 different amino acids. The principal one is cystine, which allows strong disulfate bonds to form between protein chains. This cross-linking makes hair so resistant to chemical and biological degradation. All that sulfur in Keratin also accounts for the distinctive smell of burning hair.

Cortical Fusi

Irregularly shaped air spaces in the cortex

Undulation

In hair morphology, slight waviness

Micrometer

One millionth of a meter or one thousandth of a millimeter

Anagen Phase

Period of growth in the hair cycle, averaging 3 to 5 years

Catagen Phase

Intermediate period of hair growth, lasting about 3 weeks.

Telogen Phase

Final phase in hair growth, resulting in the loss of hair over about 3 months

Interference Patterns

Patterns that demonstrate the wave nature of light, resulting from constructive(additive) and destructive combinations of light waves. This happens when a small object deflects coherent light so the wave fronts travel different directions. This phenomenon is called diffraction.

Melanin

A natural pigment found in the skin. Ultraviolet rays in sunlight make it more concentrated, causing tanning

Association

A link between an unknown sample and known evidence.

Questioned

Term used in forensics to describe a sample of unknown origin; for example, a hair was found on a jacket, but we do not know whose head it came from.

Exemplar

Term used in forensics to describe a sample of known origin; for example, a hair was found on a jacket, but we do not know whose head it came from.

Metabolite

A specific product of a substance, formed by chemical processes in the body

False Positive

A test result that comes out positive when it should not; often caused by contamination or lack of a running control.

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