Chain of custody is probably the most important part of a hair test. It is even more critical than the analysis itself because this is the proof by at least two independent witnesses that the sample provided is taken from the person who is subject to the test.  Authenticity and time and date of collection are as important as the test results.

The hair sample taken during a hair drug test is thoroughly washed before it is subject to analysis to remove any external contamination and skew the test.  This is just a precautionary move because any external contamination would just be detected as the drug itself and not the drug metabolite which could only be produced after the person’s body had processed the drug in question.

The standard hair test consists of the testing facility removing a one and one half inch segment of hair from the scalp.  Since the average person’s hair growth is approximately one half inch of hair per month the one and a half inch segment represents a ninety day period for which the subject’s activities are to be tested. The most recent one to two weeks of activity will not be present because it takes that much time for the blood flow into the hair to carry in the toxins.  The amount of hair gathered should be approximately one hundred strands of hair or the equivalent width of the tip of a shoelace tip.  If there is not enough hair on the head then a sample may be taken from the body, most likely the underarm or chest, arm or leg hair.