[Cannabis-related flash-back, a medico-legal case]

Cannabis is a psychoactive drug more and more widely consumed in industrialized countries and in the world. Amongst the numerous effects it can induce, flashback phenomena have been scientifically recognized only since the 70's. This case regards a young man who offended a friend without any objective reason. The report of the forensic psychiatrist demonstrated that the offense was committed under the influence of a cannabis flashback. The last time the offender had consummed cannabis, probably from Netherland, was two weeks before the acts. A plasmatic detection was realized and showed a level at 6 ng/mL, thirty minutes after the beginning of the flashback. This case confirms the clinical entity of cannabis flashback and gives an exceptional indication on THC blood concentration at the time of the relapse. But the pharmacokinetics of the phenomenon are largely unknown and long term studies concerning the metabolism, not only of THC but also of its metabolites, are needful. On the forensic standpoint, the possible participation of flashback phenomena must not be neglected when grounds of unexplained accidents or crimes are searched.