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.
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 average hair sample submitted as evidence ranges anywhere from 24 to 50 pieces. There are various ways to collect a sample of hair that can be used as evidence.
Hair can be considered class evidence or individual evidence, depending on how the hair was found. Individual evidence if the hair has the follicle and class evidence if the hair doesn't have a follicle.
The main physical proprieties of the hair depend mostly on its geometry; the physical and mechanical properties of hair involve characteristics to improve: elasticity, smoothness, volume, shine, and softness due to both the significant adherence of the cuticle scales and the movement control (malleability), as well as ...
Each hair has a hair shaft and a hair root. The shaft is the visible part of the hair that sticks out of the skin. The hair root is in the skin and extends down to the deeper layers of the skin. It is surrounded by the hair follicle (a sheath of skin and connective tissue), which is also connected to a sebaceous gland.
The body area from which a hair originated can be determined by general morphology. Length, shape, size, color, stiffness, curliness, and microscopic appearance all contribute to the determination of body area. Pigmentation and medullar appearance also influence body area identification.
Hair samples for DNA analysis will be gathered by laboratory personnel or law enforcement officials or a forensic examiner. For DNA testing, the hair must include the root. This requires that the hair be plucked, not cut.
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.
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.
Human hairs are generally consistent in color and pigmentation throughout the length of the hair shaft, whereas animal hairs may exhibit radical color changes in a short distance, called banding. The distribution and density of pigment in animal hairs can also be identifiable features.
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.
"Our hair follicle contains nucleic acid DNA, while our hair shaft contains mitochondrial DNA.
Fragmented Nuclear DNA Is the Predominant Genetic Material in Human Hair Shafts.
In contrast to nuclear DNA, mitochondrial DNA is more readily recoverable from hair shafts, where mitochondrial DNA has greater copy numbers. Recoverability also results from the additional mitochondrial membrane, which somewhat protects this genetic material from degradation.
Because hair can be grouped into three different racial groups it can be used to identify if it came from someone of European, Asian, or African ancestry. As such, hair can be used to exclude people of certain racial group as suspects or as having been at a crime scene.
Hair is considered class evidence and is useful in backing up other circumstantial evidence, such as by placing someone at the crime scene.
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.
Hair Shaft and Evidence Type
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.
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 ...
Hair analysis can be performed to determine if two people are related through blood. Hair structure and DNA from cells adhering to the root of the hair can be used in forensic hair analysis to assist identifying a culprit. Hair samples are examined under a microscope after being tested with particular substances.
It keeps us warm by preserving heat. Hair in the nose, ears, and around the eyes protects these sensitive areas from dust and other small particles. Eyebrows and eyelashes protect eyes by decreasing the amount of light and particles that go into them.
Your hair is made of keratin, the same protein in fingernails and toenails. And you have two types: Vellus hair is the short, fine, almost invisible hair that grows on much of your body, while terminal hair is thicker and longer and grows in places like your scalp and armpits.
Hair Suitability for DNA Testing – To test a hair for nuclear DNA, the hair must have tissue attached to the root end. If there is no root tissue, then the alternative is to test for mitochondrial DNA found within the shaft of the hair itself.