Other Stuff about hair and Fiber Analysis

History

French scientist Edmond Locard discovered that people constantly pick up and transfer bits of dust, hair, fibers and other "trace" material without being conscious of it. Locard realized that these material exchanges were key to analyzing a crime scene, and the "Locard Exchange Principle" became the foundation of forensic science in the early 1900s.

German pathologist Rudolf Virchow later showed that hairs were not unique enough to positively match a particular suspect to a particular victim.

In the United States, Paul L. Kirk established the fundamentals of microscopic hair analysis used by scientists today, and his groundbreaking textbook, "Crime Investigation," is still an important text in criminal investigation.

Significance

• Hair is easy to transfer from one person to another. It clings to furniture, carpets and clothing, and it can last for years without decomposing. These characteristics make the hair left at a crime scene an important aspect of trace evidence. Even if a suspect tried to clean up the crime site, she would most likely leave hair behind.

  Hair is easily analyzed with modern technology, like polarized light microscopes, which bring out the color and details of a hair specimen; and comparison microscopes, which allow the scientist to analyze two pieces of hair evidence side-by-side.

Function

• Hair analysis helps investigators identify individuals involved in a crime scene. Analysts first determine whether the hair came from the victim, a suspect or an animal. If the trace hair is human and matches the hair of the victim, it may help to identify the victim. If the trace hair does not belong to the victim, it may belong to the criminal. In that case, it may provide information about the relationship between the perpetrator and the crime scene, and between the perpetrator and the victim. It may also eliminate a particular suspect, thereby exonerating him.

Comparison

The forensic analyst compares the trace hair sample taken from the crime scene with another sample from a known source, either the victim or a suspect. The samples have to come from the same area of the body, generally either from the head or the pubic area. Analysts will look at the two samples through a comparison microscope to determine if there are any matches in their shafts' medullas, cortices or cuticles. If the hair follicle is still attached to the specimen, a DNA analysis might reveal the exact identity of the criminal.

Considerations

• Forensic hair analysis has limitations. Humans share hair characteristics, like color and texture, so hair alone cannot positively identify someone as a perpetrator. Hair analysis can point to a suspect, but, without DNA evidence, forensic analysis alone cannot state positively that a specific hair sample came from one particular individual and not another. Even if the trace hair matches the known hair sample from a suspect, it would probably also match samples from many other individuals. But even with this limitation, forensic hair analysis is considered one of the most valuable tools available to crime investigators.

Read more: Forensic Analysis of Hair | eHow.com http://www.ehow.com/about_5597295_forensic-analysis-hair.html#ixzz1epM1htwv