Hair analysis as evidence in forensic cases.

Because hair analysis can be used for the determination of drug use months after drug consumption, hair analysis data can often act as important and even decisive evidence in the courtroom. More recently developed GC/MS methods offer excellent sensitivity and can make the distinction between chronic heroin and codeine use, which was not possible earlier with radioimmunoassay techniques. From more than a thousand hair analyses, the morphine/codeine ratios necessary to determine heroin use were set at 5:1 for low morphine concentrations (< 1 ng/mg hair) and 2:1 for concentrations above 1 ng/mg hair. The distinction can be further focused with the additional analysis of the metabolite monoacetylmorphine (MAM). As can be seen from several case examples, hair analysis cannot pinpoint an exact date of opiate use, but it can be used to validate or invalidate a subject's statement concerning his/her drug consumption. Interpretations should always be made cautiously. Ranges, means and medians are also listed for amphetamine, cocaine and cannabis and work is under way to draw similar safety guidelines for these drugs.