The role of benzodiazepines in violence is known for a long time but this kind of behaviour could happened in various circumstances. A scientific review don’t well discern side effect from paradoxical reaction, behavioural desinhibition,…Are there the same mechanisms that contribute to these aggressions, according to normal use, misuse or abuse (with or without alcohol or other drugs)? A study is led, starting from 140 criminals presenting a psychiatric pathology. Among them, 68 had absorbed a benzodiazepine before committing their crime. The cases, all of them hospitalized in ‘;unites pour maladies difficiles” (special hospitals) in France, tend to prove that the pathological mechanisms are numerous. The legal and ethical implications are very complex. The conclusion of this study seems to reveal a special link between the accomplishment of a crime and the benzodiazepine use, abuse and dependence.