Characteristics within these regions are used to determine whether the hair is human or animal, racial origin and body area. A microscopic hair examination can also determine if a hair was forcibly removed, artificially treated or diseased.
Hair Microscopy
This examination routinely involves a two-step process—the identification of questioned hairs and the comparison of questioned and known hairs.
Variability in such features can help forensic scientists to determine age, gender, and racial origin of the person that shed the hair, as well as allowing one to determine which area of the body hair has come from.
The forensic analysis of hair evidence can be extremely valuable in the examination of physical evidence by (1) demonstrating that there may have been an association between a suspect and a crime scene or a suspect and a victim or (2) demonstrating that no evidence exists for an association between a suspect and a ...
It helps to protect us from the elements, to regulate our body temperature, and to perceive sensations. The amount of hair on a person's head can vary by individual. The average human head has about 100,000 hairs with a similar number of hair follicles.
Hair - Analysts can tell investigators if individual hairs are human or animal, and in the case of human hair, where on the body the sample originated. Samples can be tested to determine the color, shape and chemical composition of the hair, and often the race of the source individual.
Characteristics within these regions are used to determine whether the hair is human or animal, racial origin and body area. A microscopic hair examination can also determine if a hair was forcibly removed, artificially treated or diseased.
2): The following are some of the distinguishing features. Length: Human scalp hairs are longer than most animal hairs. Diameter: Human hairs are usually in the range of 0.05-0.15 mm; animal hairs can be narrower or coarser.
Although hair is routinely collected at the scene of a crime, these days it is considered unreliable and rarely used as forensic evidence – especially after the FBI acknowledged that its testimony on microscopic hair analysis was flawed in at least 90% of cases.
The functions of hair include protection, regulation of body temperature, and facilitation of evaporation of perspiration; hairs also act as sense organs. Hairs develop in the fetus as epidermal down growths that invade the underlying dermis.
Until now, forensic scientists have only been able to extract DNA from hairs found at crime scenes if they have their root attached. Unfortunately, most hairs do not have the root attached, so using DNA sampling to discover whom it belonged to has been impossible.
Hair evidence can provide information about the race of the individual, and it can also show if the hair has been chemically treated, or if has been cut or pulled out in a certain way. Hair evidence can also show where in the body it was located, as well as genetic information such as blood type or DNA.
Hair is considered class evidence and is useful in backing up other circumstantial evidence, such as by placing someone at the crime scene.
A hair follicle consists of two main layers, an inner (epithelial) root sheath and an outer (fibrous) root sheath. At the base of the hair follicle is the hair bulb, which houses the dermal papillae and hair matrix cells. The hair bulb and inner epithelial layer generates hair.
A sharp change in color near the proximal (root) end of the hair indicates that the hair is dyed, as does coloration that is relatively evenly distributed throughout the cortex. Note if the hair appears to have been bleached (overall yellowish tinge to the cortex), dyed, or otherwise treated.
Using characteristics such as color, curliness, and thickness may help identify different human hairs.
- Cuticle in humans is imbricated; and the cuticle in animals is coronal or spinous. - Pigmentation in animal hair is denser than human hair. - Animal hair can change colors in banded patterns; human hair cannot.
Many things can be determined by using microscopic hair examination. These include how the hair was released from the scalp (naturally or with force), how the hair was typically cut (razor or scissors), hair color, and ancestry (European, Asian, or African).
A strand of hair cracked California cold case. Diane Dahn was stabbed to death in her California home in 1988, authorities said. A strand of hair helped crack her case almost 34 years later. Dahn's body was found in her apartment in Santee by a co-worker, the San Diego County Sheriff's Department said in a news release ...
A new forensic technique could have criminals—and some prosecutors—tearing their hair out: Researchers have developed a method they say can identify a person from as little as 1 centimeter of a single strand of hair—and that is eight times more sensitive than similar protein analysis techniques.
The hair shaft (main part of the hair) is considered class evidence but if the root is intact and DNA can be collected then it is individual evidence. Because most hair collected is class evidence, it is not possible to prove that it came from a particular person.
They are pliable and resilient, and recover from repeated mechanical deformations with little loss of their physical properties. Vestigial as it is, human scalp hair has retained all these valuable characteristics.
Facts and Statistics About Hair
Hair is made mostly of a protein called keratin. Human facial hair grows faster than any other hair on the body. On average, we lose 50 to 100 strands of hair a day from the scalp. Human hair grows faster in warm weather because it stimulates hair growth.