morphology of hair
Hair is an appendage of the skin that grows out of an organ known as the hair follicle.
� The length of a hair extends from its root or bulb
embedded in the follicle, continues into a shaft, and terminates at a tip end.
� It is the shaft, which is compose
cuticle
The cuticle is the scale structure covering the exterior of the hair.
- The scales always point towards the tip of the hair. - The scale pattern is useful in identification. - Three basic patterns; cornal, spinous and imbricate
cortex
The cortex is the main body of the hair shaft.
- Its major forensic importance is the fact that it is embedded
with the pigment granules that impart hair with color.
- The color, shape, and distribution of these granules provide the criminalist with impor
medulla
The medulla is a cellular column running through the center of the hair.
� The medullary index measures the diameter of the medulla relative to the diameter of the hair shaft.
� For humans, the medulla generally occupies less than one-third the diameter o
root
The hair root is determined by hair's current growth phase:
- Anagen phase- growth 1-6 yrs - Catogen phase- middle phase decreasing rate of growth - Telogen phase- final phase in which the hair will fall out
� When pulled from the head, some hairs in the
comparing strands
The comparison microscope is an indispensable tool for comparing the morphological characteristics of hair.
� Scale structure, medullary index, and medullary shape are particularly important in animal hair identification.
� When comparing strands of human
comparing strands
The most common request is to determine whether or not hair recovered at the crime scene compares to hair removed from the suspect.
� However, microscopic hair examinations tend to be subjective and highly dependent on the skills and integrity of the anal
questions for the hair examiner
Can the body area from which a hair originated be determined?
�Huge variations
� Can the racial origin of hair be determined?
�Generally yes but there are exceptions
� Can the age and sex of an individual be determined from a hair sample?
�only a distinct
hair and dna
Recent major breakthroughs in DNA profiling have extended this technology to the individualization of human hair.
� The probability of detecting DNA in hair roots is more likely for hair being examined in its anagen or early growth phase as opposed to its
hair and mitochondrial dna
Mitochondrial DNA can be extracted from the hair shaft.
� Mitochondrial DNA is found in cellular material located outside of the nucleus and it is transmitted only from the mother to child.
� Mitochondria- bacterial origin, first symbiotic relationship be
collection and preservation
Forensic hair comparisons involve either head hair or pubic hair.
� The collection of 50 full-length hairs from all areas of the scalp will normally ensure a representative sampling of head hair.
� A minimum collection of 24 full-length pubic hairs should
types of fibers
(Locard's Exchange principal )
� Natural fibers are derived in whole from animal or plant sources. For example:
- Wool - Mohair - Cashmere - Furs - Cotton
� Manufactured fibers- man made. - Regenerated fibers are manufactured from natural raw
materials an
fiber evidence
The quality of the fiber evidence depends on the ability of the criminalist to identify the origin of the fiber or at least be able to narrow the possibilities to a limited number of sources. The forensic value of fiber evidence is its diversity in our en
methods for comparison
The microspectrophotometer is a combination of a traditional light microscope and a spectrophotometer. It allows a forensic analyst to view an object under a microscope while simultaneously obtaining its visible of infrared absorption pattern.
� The micro
fiber collection and preservation
The investigator's task of looking for minute strands of fibers often becomes one of identifying and preserving potential "carriers"of fiber evidence.
� Relevant articles of clothing should be packaged carefully in separate paper bags.
� If it is necessar