The consumption of alcohol mixed with energy drinks (AmED) has become popular in Australia, particularly among young people. AmED research suggests there are associations between AmED consumption and harmful behaviours, including criminal offences. This study investigated the behaviours of a group of AmED consumers known to engage in high-risk activities—police detainees. It found most detainees had recently consumed energy drinks, but consumption of AmED was less common than in community samples.The study also compared the behaviours of AmED consumers with alcohol consumers, and analysed how AmED consumers behaved in AmED sessions versus alcohol sessions. It found AmED consumers reported drinking more alcohol in a usual alcohol session than in a usual AmED session. AmED consumers were also significantly less likely to report being assaulted or committing a traffic offence in an AmED session, compared with an alcohol only session.