Samples from a self-proclaimed cocaine (COC) user, from 19 drug users (postmortem) and from 27 drug chemists were extensively washed and analyzed for COC, benzoylecgonine, norcocaine (NC), cocaethylene (CE) and aryl hydroxycocaines by liquid chromatography-tandem mass spectrometry. Published wash criteria and cutoffs were applied to the results. Additionally, the data were used to formulate new reporting criteria and interpretation guidelines for forensic casework. Applying the wash and reporting criteria, hair that was externally contaminated with COC was distinguished from hair collected from individuals known to have consumed COC. In addition, CE, NC and hydroxycocaine metabolites were only present in COC users' hair and not in drug chemists' hair. When properly applied, the use of an extended wash, along with the reporting criteria defined here, will exclude false-positive results from environmental contact with COC.
