Hair can be used for a DNA profile.
Apparently ions help the hair dry faster with less heat, which can damage hair. I'm not sure there's a lot of evidence to support it, though.
Hairs can be used to detect DNA of the killer or to identify the victim. Hairs can also be tested for poison.
For women of all ages, pigtails are a practical style that help to keep hair healthy. However, there is no evidence that any style of hair can be used to actually help hair grow faster or in greater volume.
Evidence doesn't "expire". As long as the sample is in suitable condition to allow analysis, it can be used forever.
It is not it just simply is not
-.-
DNA
We cannot identify a person specifically with hair alone. Even if their is mtDNA, it isn't good enough-DNA is class evidence anyway.
Root of the hair containing protoplasm
Anything can be used as evidence if it is obtained in a legal manner. Therefrore text message can be used as evidence if the evidence was legally obtained.
There is no evidence of a link.
Hair containes DNA evidence and can also be tested for drug usage.