Chapter Learning Objectives • Hair is class evidence. • Hair can be used to back up curcumstantial evidence. • Hair absorbs substances within the body and from the external environment.
Locard Exchange Principle • Hair is considered class evidence and is useful in backing up circumstantial evidence. • Locard Exchange Principle states there is always a cross transfer of evidence between suspect and victim
Human Hair • Hair is made up of protein polymers. • The hair shaft is composed of 3 parts – the cuticle (outer), the cortex (middle), and the medulla (core). • The cortex is made of keratin.
Animal hairs • Animal hairs show a wide variety of medullar patterns
Human hair growth • The diameter of human hair is 25-125 um. • Human hair grows about 1 cm per month. • The root can be important in classifying hair. • The 3 stages of growth are; • Anagen phase – averages 3-5 years • Catagen phase – intermediate phase lasting 3 weeks • Telogen phase – final phase of growth