I quit smoking Marijuana on May 31, 09 because I was being forced by my employer to comply with a chemical dependency program in order to keep my job. I have not used since that time. My body tested negative through urine for the first time about two weeks ago. Can I subtantiate that I have been in compliance the entire time by a hair follicle test and if so how does that work?

Hair Follicle Drug Testing FAQ - Hair Testing Facts

Quoted from the site:
Q:What time does a standard hair follicle test cover?
A standard hair follicle screen covers a period of approximately 90 days, but is susceptible to time variation depending on the growth rate of your hair. The hair sample is cut as close to the scalp as possible and the most recent 3.9cm (or 1.5 inches) are tested. It is possible to go back even further than 90 days since the time is limited only by the length of the hair sample, but is standardized to a 90 day history.

Q:What type of drugs can be detected in a standard hair test?
Cocaine (Cocaine & Benzoylecgonine), Marijuana, Opiates (Codeine, Morphine & 6-Monacteyl Morphine), Methamphetamine (Methamphetamine/Amphetamine & Ecstasy), and Phencyclidine (PCP). These five drug classes are mandated for testing by the Federal Government.

Q:How fast does head hair grow?
Hair collected at the crown of the head grows on the average of approximately 1.3 cm (or 1/2 inch) per month. This growth rate varies among people by approximately + .2 cm per month which can create a possible time variation of up to +1 week per month.