Bioanalytical procedures for detection of chemical agents in hair in the case of drug-facilitated crimes

Pascal Kintz

The use of a drug to modify a person's behavior for criminal gain is not a recent phenomenon. However, the recent increase in reports of drug-facilitated crimes (sexual assault, robbery) has caused alarm in the general public. The drugs involved can be pharmaceuticals, such as benzodiazepines (flunitrazepam, lorazepam, etc.), hypnotics (zopiclone, zolpidem), sedatives (neuroleptics, some anti-H1) or anaesthetics (gamma-hydroxybutyrate, ketamine), drugs of abuse, such as cannabis, ecstasy or LSD, or more often ethanol. To perform successful toxicological examinations, the analyst must follow some important rules: (1) obtain as soon as possible the corresponding biological specimens (blood and urine); (2) collect hair about 1 month after the alleged event; (3) use sophisticated analytical techniques (gas or liquid chromatography coupled to tandem mass spectrometry, MS/MS, headspace gas chromatography); and (4) take care in the interpretation of the findings. Drugs used to facilitate sexual assaults can be difficult to detect (active products at low doses, chemical instability), possess amnesic properties and can be rapidly cleared from the body (short half-life). In these situations, blood or even urine can be of low interest. This is the reason why some laboratories have developed an original approach based on hair testing. Hair was suggested as a valuable specimen in situations where, as a result of a delay in reporting the crime, natural processes have eliminated the drug from typical biological specimens. While there are a lot of papers that have focused on the identification of drugs in hair following chronic drug use, those dealing with a single dose are very scarce. The experience of the author and a review of the existing literature will be presented for cases involving benzodiazepines, hypnotics, gamma-hydroxybutyrate and various sedatives or chemical weapons. The expected concentrations in hair are in the low picogram/milligram range for most compounds. Hair analysis may be a useful adjunct to conventional drug testing in sexual assault. It should not be considered as an alternative to blood and urine analyses, but as a complement. This approach may find useful applications, but the definition of legally defensible cutoff values would require much more data. MS/MS technologies appear as a prerequisite in drug-facilitated cases.