Definitions
Undesirable events in the area of public order, criminality, and controllability were defined in similar terms as those in the area of medical safety. A public order event was considered to be relevant if it represented an untoward and/or serious event, which was at least possibly causally related to the execution of the study. Analogous to the scale used in the area of medical safety, the degree of causality between the event and the conduct of the study was rated as "certainly", "likely", "possibly", "certainly not" and "unknown". In addition, the severity of the event was defined as mild, in case the event caused a small and short disturbance in the treatment site or in the surroundings of the treatment site, moderate, if the disturbance was moderate, and severe, if the event resulted in a considerable and/or long-lasting disturbance of the public order and controllability. In case of a (failed or succeeded) attempt to take prescribed heroin out of the treatment site, the severity of the event was rated as mild to moderate, if it concerned an amount of heroin smaller than, or equal to the participant's total dose of that day, and severe, if a larger amount of prescribed heroin was involved.

Registration and reporting
To assure that events and complaints, related to public order, controllability, and public safety, were correctly registered and handled, a local complaints office was installed in each participating city, where citizens could report an event or complaint, related to the conduct of the study. In some cities, the complaints office was installed especially for the present trials, whereas in other cities, an existing police station in the surroundings of the treatment site served as the complaints office. Residents who lived in the direct environment of the treatment site could report their complaint directly to the treatment site. Lastly, events that occurred within the treatment site (e.g. aggressive behavior, attempts to take heroin out of the treatment site) were registered directly by the treatment staff as well.

In all cities, the staff working at the complaints office were instructed about the procedures used to register and evaluate the complaints. Events and complaints that were judged to be severe by the staff of the complaints office had to be reported to the treatment site within 24 hours. In addition, severe and/or untoward events and complaints had to be reported to the monitoring organization. The monitoring organization subsequently sent a written confirmation of the receipt back to the complaints office, and within 48 hours to the National Research Board of the CCBH. All severe events and complaints that were judged to be at least possibly causally related to the execution of the study, were reported within 48 hours to the National Committee on Public Order and Controllability (LCB) (see paragraph 2.7). This report had to be accompanied by information about the involved treatment site, and a detailed description of the event or complaint, in terms of its nature and background, and - where possible - its causal relation with the execution of the study. Lastly, routine overviews of all events and complaints were sent on a monthly basis to the LCB.