Following closely behind levels in Western countries, the number of drug-facilitated sexual assaults (DFSAs), involving the illicit use of medicine, has been recently increasing in Japan. Tirazolam is the most frequently used date-rape drug in DFSAs occurring in Japan. In this study, the effect of triazolam on behavior in response to fear and anxiety was evaluated using an elevated plus-maze test in mice. Triazolam-treated animals (0.01 mg/kg) showed no significant difference in total locomotor activity compared with vehicle-treated mice (controls). On the contrary, activity levels on the open arms of the apparatus (time spent, mean value of movement), where mice would normally feel anxiety or fear, were significantly increased in triazolam-treated mice compared with controls. However, total locomotor activities on the plus-maze were not different between two groups, indicating that sedation was not induced by tirazolam under these conditions. These results suggest that triazolam treatment led the mice to become insensitive to fear and anxiety; their defence reactions were impaired. We conclude that this finding provides scientific evidence in reply to defence arguments presented in court trials that there is little or no evidence of the victim attempting to escape from a sexual assault. Additionally, the finding is as true of other benzodiazepine receptor agonists as of triazolam.