ABSTRACT
The devil is in the details, and there are many details concerning the analysis of hair for drugs of abuse and the interpretation of the analytical result. Several controversies have arisen over the years surrounding a number of these details on analysis. The controversies have focused on three broad areas: (1) the mechanisms for appearance and binding to hair of drugs of abuse, (2) removal of external contamination, and (3) bias. The conclusions reached in these three areas and the weight given to the scientific facts greatly color the interpretation of any hair analysis result. This review outlines the historical evidence accumulated in these three areas of research and discusses how the interpretation of these data has led to two dissimilar models of incorporation and removal of drugs from hair. Also, new data are presented to clarify areas of controversy and show how some of the variables of cutoffs, bias, passive exposure, and decontamination are closely related. An understanding of the data and its interpretation is critical to the proper application of hair analysis results.
