"Hair analysis is a test in which a sample of a person's hair—typically from the back of the neck—is sent to a laboratory for measurement of its mineral content. This discussion concerns multielemental hair analysis in which a single test is used to determine values for many minerals simultaneously. This type of analysis used by chiropractors, "nutrition consultants," physicians who do chelation therapy, and other dubious practitioners who claim that hair analyses can help them diagnose a wide variety of diseases and can be used as the basis for prescribing supplements."
Stephen Barrett, M.D. Here is the full article on the Quackwatch website
This article is actually a load of biased rubbish. This and several similar ones are routinely rolled out to discredit the Hair Tissue Mineral Analysis as a valid forensic tool for assessing nutrient status and heavy metal exposure.