From 1991 to 1998 he was researcher and consultant at the PIOV Research Centre Public order and Safety (Hoogerheide, the Netherlands), where he co-ordinated research on public order policing, use of force, pepper spray, bomb-threats and crisis management. Between 1998 and 2004 he was research manager at the LSOP Police Knowledge and Education Centre (Apeldoorn, the Netherlands), where he initiated a research programme "Managing Dangerous Situations", which focuses on interactions between the police and the public in potentially violent or dangerous situations. He was one of the organisers of the First European Conference on Hostage Negotiations held in November 1998 in Doorwerth (near Arnhem).