The takeaway. Hair follicle drug tests can identify drug use up to 90 days prior to the test date. That's because the chemicals from the drugs that end up in your bloodstream become part of the hair cells as your hair grows. Hair follicle drugs tests may not be appropriate for determining recent drug use.
The hair follicle at the base of human hairs contains cellular material rich in DNA. In order to be used for DNA analysis, the hair must have been pulled from the body -- hairs that have been broken off do not contain DNA. Urine itself does not contain DNA, but it may contain epithelial cells, which do contain DNA.
Physical evidence is comprised of those forms of data that can be measured or quantified. Examples include fingerprints, accelerants, hair or fibers, etc.
Hair suitability for DNA examinationsNuclear DNA analysis can be done on human hairs. The trace section assists the DNA section by screening hairs and determining their suitability for DNA testing. A microscope is used to examine the root end of the hairs, in order to determine if they are suitable.
The value of hair evidence is related to the variability of hair characteristics between individuals in the population, which can be visualized through the use of comparison microscopy. This enables the hair examiner to compare the microscopic characteristics of the known and questioned hairs in one field.
The hair shaft is the part of the hair that is above the skin. These cells attach themselves to antigens that invade damaged skin and alert the immune system to their presence. A melanocyte is a cell that produces melanin, and is located in the basal layer of the epidermis.
Hair is considered class evidence and is useful in backing up other circumstantial evidence, such as by placing someone at the crime scene.
The most common methods used to collect hair and fiber evidence include the following:
- Visual collection. On some surfaces, hairs and fibers can be seen with the naked eye.
- Tape lifting. Trace tapes are available for the collection of trace hair and fiber evidence.
- Vacuuming.
Comb the individual's hair over clean white paper using a clean fine-tooth comb. Carefully fold the paper together with the comb into a bindle to prevent loss of any trace evidence. Place the bindle in an envelope and label with appropriate information.
Although the science of microscopic hair examination can never result in an identification, that is, conclude that a hair came from one individual to the exclusion of all others, the vast amount of both macroscopic and microscopic information available from hair analysis can provide a strong basis for an association
Explain how and when hair is considered as class evidence, and when it's considered individual evidence. Hair is considered class evidence when the follicle is not attached because the follicle is the part that contains DNA. When the follicle is attached, it is considered individual evidence.
As discussed previously, fibers are considered a form of trace evidence that can be transferred from the clothing of a suspect to the clothing of a victim during the commission of a crime. Fibers can also transfer from a fabric source such as a carpet, bed, or furniture at a crime scene.
The easiest method is called dusting, in which you use a very fine powder that can stick to the oil in the fingerprint. Once the fingerprint becomes visible, you can lift it from the surface with clear tape and transfer it to another surface to then take into the laboratory to analyze further.
The cortex of the hair shaft is located between the hair cuticle and medulla and is the thickest hair layer. It also contains most of the hair's pigment, giving the hair its color. The pigment in the cortex is melanin, which is also found in skin.
Like hair, fibers are considered class evidence. Fibers have probative value because they can create connections, or associations. For example, a suspect may deny he was ever in a particular place or ever in contact with a particular person.
A further consideration with respect to hair testing is the sensitivity of the test. The test will not detect single use of a drug.
In a paper published on Sept. 7, a team led by researchers at the Lawrence Livermore National Laboratory in California demonstrated that they are able to identify individuals by unique proteins found in hair. At present DNA is the highest bar for identification in forensics.
Hair is considered class evidence. Alone (without follicle cells attached), it cannot be used to identify a specific individual. In the best case, an investigator can identify a group or class of people who share similar traits who might share a certain type of hair.
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 downgrowths that invade the underlying dermis.
A hair pull test is used for monitoring advancing alopecia areata, acute cases of telogen effluvium, anagen effluvium and loose anagen syndrome, and if more than 10% of hairs in a pulled bundle are removed, the results are considered positive. The test is conducted at four locations on the scalp.
Infections of the scalp include bacterial infection of hair follicles (folliculitis), infestation of head lice (pediculosis capitis), and fungal infection of scalp ringworm (tinea capitis). Itching and excessive flaking of the scalp is seen with both dandruff (seborrheic dermatitis) and psoriasis.
The hair pull test will be positive where the hair is thinning, but negative away from the thinning areas. Patients with hair shedding may have telogen effluvium or diffuse alopecia areata, both of which cause a positive hair pull test.
Your hair could be straight at the root and wavy at the ends. The key is to understand what each
type needs so you can style it well and keep it healthy.
What types of hair are there?
| Type 1 | Straight hair |
|---|
| Type 2 | Wavy hair |
| Type 3 | Curly hair |
| Type 4 | Coily hair |
Tests for Hair Loss in Women
- Hormone levels (DHEA, testosterone, androstenedione, prolactin, follicular stimulating hormone, and leutinizing hormone)
- Serum iron, serum ferritin, and total iron binding capacity (TIBC)
- Thyroid levels (T3, T4, TSH)
- VDRL (a screening test for syphilis)
- Complete blood count (CBC)
If it dries straight without a bend or curl, then your hair is straight (or type 1, as it is commonly referred to). If it dries with a slight curve or “S” shape, then it is considered wavy (type 2).
Genetic factors appear to play a major role in determining hair texture—straight, wavy, or curly—and the thickness of individual strands of hair. Studies suggest that different genes influence hair texture and thickness in people of different ethnic backgrounds.
The scalp is usually described as having five layers, which can conveniently be remembered as a mnemonic: S: The skin on the head from which head hair grows. It contains numerous sebaceous glands and hair follicles. C: Connective tissue.
At any given time, a random number of hairs will be in one of three stages of growth and shedding: anagen, catagen, and telogen.
