Hairs

• its found on all humans and animals • it is constantly being produced and shed • it is easily overlooked by criminals • it is readily transferred from one person/object to another person/object • highly stable - resisting both physical and chemical degradation • can be distinguished from each other and with DNA testing

All true hairs have the same basic chemistry

• used to identify locations where an individual may have travelled based on changes in drinking water isotopes in different locations • similar uses to link substances of abuse

• lanugo • vellus • terminal

• hairs that are formed in utero • fine and unpigmented • typically shed before or shortly after birth

• fine, short, unpigmented/lightly coloured • on almost all skin surfaces (forhead, nose, ears, bald scalp) • not found on palms of hands or soles of feet

Macroscopically visible on children and adults 1. primary - head, eyelash, eyebrow 2. secondary - pubic, underarms, beard

• cuticle - outermost layer • cortext - main bulk of hair • medulla - innermost layer of hair shaft

chemical resistance

mechanical properties * contains most of the pigment granules giving hair its colour

not well understood * not present in all hairs

• anagen - active growing phase of hair extending progressively from the follicle root outwards • catagen - transition phase when growth slows and eventually stops • telogen - resting phase when minimal force is required to remove hair and natural shedding occurs

Pigment stops being produced

• for individual hairs forceps can be used • tape lift can be used to remove the pressure when using forceps - most efficient when collecting hairs from large surfaces • combing • 20 hairs from 5 head regions should be collected and packaged separately - plucking and combing (gives variation)

• gross examination, recovery and collection • preliminary evaluation of physical characteristics • microscopic techniques • DNA • SEM (sometimes TEM) - morphological features • spectroscopic techniques - IR and Raman • chromatographic techniques and MS

• optical: stereoscopic, reflected light, comparsion, fluorescence, brightfield, polarised • SEM and TEM

• macroscopic colour • length • general contour and curliness • approximate diameter

• colour • cosmetic treatments • cross-sectional shape • biological damage • adhering material • thickness range • general damage • non-root morphological

• colour • pigment granules • inner margin • thickness • damage • scale protrusion

• pigment granules - density, size, shape • texture • appearance of medulla • root features if present - growth stage, follicular material, abnormalities

• head hairs have the most discriminative value • results of a microscopical hair comparision must be completed with a second examiner and should be blind to initial conclusions • final analysis unless more detail is required or root requires evaluation to explore DNA testing

• employed when further analysis is required • can examine the surface of hair to highlight scales or physical damage to the hair • combined with SE, BSE and EDX modes - provide elemental data about hairs or residues

• used to distinguish hair treatments and chemical damage along the length of hair • possible to distinguish between dye colour and brands • chemometrics and strong training required

• employ a first mass analysis stage to select a precursor ion • then excite this selected ion species (usually by collosion with a neutral target gas) • this causes it to fragment further to give one or more product ions plus neutral fragments • then employ a second mass analysis stage to determine the mass spectrum of the product ions