Schizophrenic patients with a substance abuse condition present one of the highest risks for violent behaviour. The traditional safety measures used in psychiatry are still in force but challenged by a trend to avoid all involuntary action, in respect of patient autonomy. There is an urgent need to develop strategies to cope with this situation, which is especially difficult to cope with in case of first encounters with dual diagnosis patients in psychiatry. The risk for open aggressiveness is difficult to assess and to manage in first encounters, avoiding an escalation and working a deescalation strategy. The strategy described in this paper is based on a distinction of the different types of first encounter and on general rules.