2. Hairs and fibers Differences Similarities: Both are… March 28 - 29
Trace evidence
Class evidence - unless something really unusual
Hard to see - Easy to miss at crime scene
Collected with tape and tweezers
Examined under microscope
tube shaped
usually round
could be dyed
easily shed - so lots of them around
most common evidence at a crime scene
could give DNA - (blood on fiber or root on hair)
are made of non-living material
don't have special storage requirements
Differences
fibers can be man-made
fibers have no medulla, cuticle or cortex
fibers have no internal structures
hairs have pigment just in the center
hairs have a scaly surface
hairs can have a root
hairs can have a pointed tip
Hairs can give mitochondrial DNA
hairs can indicate race
some fibers don't stink when burned
some fibers melt
hair is always natural
Hairs from the same person or animal are always different – there is variety
all the fibers from the same garment will be identical unless damaged