This news brief has nothing but praise.
“Dr Kintz guided the participants on how to store the sample (in an envelope); when the test is best suited to be administered (after ten days of suspected time of consuming drug), how to detect a drug that was not voluntary consumed and how to go over external and internal contamination.”
Looking for more information on hair testing I found this lab speaking its advantages over urine testing.
And in this link, there finally is discussion on the “controversies” in hair drug testing, although it is dated 2003.
And this one from 2010 dealing with 2d hand marijuana contamination.