Knock-Out Drugs: Their Prevalence, Modes of Action, and Means of Detection Dtsch Arztebl Intv.106(20); 2009 MayPMC2689633
The most frequently used drug in cases of sexual assault is still alcohol (ca. 40% to 60%), followed by illegal drugs (cannabis, cocaine). The presence of involuntarily consumed medications and drugs of abuse is demonstrated by routine toxicological analysis only in relatively few cases (ca. 2%). The substances most commonly found are benzodiazepines, followed by other hypnotics.
In Europe, the illegal substance gamma-hydroxybutyric acid (GHB, “Liquid Ecstasy”), often mentioned as a “date-rape drug,” is only rarely detected with sufficient medicolegal certainty. This may be due to its rapid elimination (it is detectable in blood for up to 8 hours, in urine for up to 12 hours) as well as its physiological occurrence in the body.
If the toxicological analysis of blood and urine is negative in a case of suspected DFSA, then the analysis of a hair sample about four weeks after the assault can detect the presence of drugs consumed at that time. If the victim has long hair, it may be possible to detect knock-out drugs taken more than four weeks earlier. In Europe, convictions for drug-facilitated crimes are comparatively rare, mainly because of the difficulty of demonstrating conclusive evidence.