- Slides: 24
Trace Evidence Hair Analysis
Trace Evidence. Physical evidence that is of such a small size that it can be unknowingly lost or transferred. Most of the time this evidence alone cannot prove ID of suspect, but can narrow the search.
Hair. Large amounts of trace evidence is hair. Some things to consider about hair as evidence. A person does not consciously loose hair. It falls off without notice. Hair is resistant to change Hair is abundant • • •
Hair will……. . l Help establish the scope of crime scene l Place suspect at the scene l Connect a suspect with a weapon l Support witness statements l Connect the crime scene areas (abduction, vehicle use, dumpsite)
Morphology. Hair is the appendage that grows out of a hair follicle. The hair follicle consists of: o Cuticle (outer) o Cortex (middle) o Medulla (center)
Cuticle- Hard outside covering made of overlapping scales. Animal Hair looks like shingles on a roof. Human hairs do not bear this characteristic.
Cortex- Spindle shaped cortical cells contains pigment granules. The color, shape, and distribution of these granules are invaluable to criminalists.
Medulla- Collection of cells that appear to be a central canal- in animals. This occupies over half of the hairs diameter. For humans, the medulla occupies less than a third of the diameter.
Root- Within hair follicle shape is based on developmental stage.
Stage 1 Anagen Phase- AKA Initial Growth Phase. Follicle is actively producing hair. Root at this point is flame shaped. When this hair is pulled a follicular tag is connected.
Stage 2 Catagen Phase- Transition between anagen and telogen. This is slower growth of hair and the root is elongated and smaller.
Stage 3 Telogen Phase- final growth phase. Hair naturally falls out of skin. The roots by this point are club shaped.
Comparison of human hair l Can detect racial origin by comparing ¡ Pigmentation ¡ Diameter ¡ Cross section www. fbi. gov
Caucasian hairs are usually straight or wavy with very fine to course pigments l Cross sections are oval to round in shape l
Hair from those of African descent is normally kinky, containing dense, unevenly distributed Pigments. *Cross sections are flat in shape
l Oriental hair is perfectly round by cross section l The diameter is straight l Pigment is dark
Sematic Origin( where on body) l Look at length l Look at texture l Tip of hair will be cut for scalp l Tip will be tapered for other areas
Cut end, Razor cut, split end, pubic
Animal hair comparison Medulla covers over ½ of the hair l The cuticle is not smooth like human, can have spineous or coronal l Medullar patterns vary. a. ladder b. Lattice c. Vacuole • Roots are interesting- deer has wine glass shape l
Comparison between animals l Cat hair/root of cat hair l Dog hair/root of dog hair