Gas chromatography-mass spectrometry detected acepromazine in the residue of one of the glasses used by the alleged sexual assault victim. No other drug was detected in this sample, and no drugs were detected in the alleged victim's blood. The absence of acepromazine in her blood was particularly verified; however, acepromazine was subsequently detected in the 0.5-2.5 cm segment of her hair collected 1 1/2 months after the assault. The drug was found at a concentration of 31 pg/mg. This was consistent with a single dose of acepromazine. In the current case, a 29-year-old woman living in a small French village in the countryside was found by a neighbor tied to the kitchen table in her house at 11:00 in the morning. She was in a drowsy state. In a subsequent statement, she reported being asleep in her bed when she was woken up by a man wearing a hood. He forced her into the kitchen where he made her drink an unknown beverage. Although she had memory lapses, she remembered having her wrists and ankles bound and being subjected to sexual caresses. Approximately 2 weeks after the assault, a suspect admitted the attack and the oral administration of acepromazine. One of the consequences of his confession was the toxicologist's recommendation for acepromazine analysis in the victim's hair in order to document the confession. The hair analysis was conducted with a liquid chromatography-tandem mass spectrometry method. 2 figures and 26 references