Analysis of Extensively Washed Hair from Cocaine Users and Drug Chemists to Establish New Reporting Criteria

Abstract

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.

Anatomy and Physiology of Hair, and Principles for its Collection

“…Proposals for discriminating between contamination and incorporated drugs have been proposed [72,73] and may provide sufficient confidence in the future to be accepted as a standardized approach but until such time, the potential role of external contamination must always be considered when interpreting positive hair tests.…”

Determination of hydroxy metabolites of cocaine in hair samples for proof of consumption

“…First studies in hair were performed looking for o ‐, p ‐ and m ‐OH‐COC . The aim of the present study was the search for hydroxy cocainics in authentic hair samples as specific markers of COC use thus enabling improvement of the criteria regarding a more valid interpretation of COC findings in hair.…”

Ethnic hair care products may increase false positives in hair drug testing

“…The relatively small amounts of drug used to contaminate these hair specimens produced contaminated hair that greatly exceeded the cut-off level to be considered positive. Forensic drug chemists, working under controlled laboratory safety conditions, have shown drug contamination in hair [25]. The hands of a cocaine or methamphetamine smoker or nasal insufflator could be less pristine.…”

“…External contamination considerations have prompted the FBI to stop testing hair for drugs [21]. Some hair testing laboratories have consistently maintained they can distinguish contamination from use [22,23] while others have found that contamination cannot be completely removed, relying on drug metabolites and/or decomposition products to determine drug use [24,25].…”