Preventing outlaw biker crime in the Netherlands or just changing the dark figure? Estimating the impact of the Dutch whole-of-government approach on outlaw biker crime using interrupted time series analysis

Confronted with growing public concern about violence and other serious crime committed by outlaw motorcycle clubs, in 2012 the Dutch government launched a whole-of-government approach to discourage club membership and organized criminal behaviour. The whole-of-government approach included a zero tolerance policy towards crimes committed by outlaw bikers and increased law enforcement and prosecutorial attention towards members of outlaw motorcycle groups (OMCG members) and their support clubs. In this study, we estimate the effects of the whole-of-government approach on the level of prosecutorial charges levied against the Dutch biker population. We do so by applying (quasi-experimental) interrupted time series analysis to the conviction data available on 1617 Dutch OMCG members and 473 support club members in four recorded crime categories: overall crime, violent crime, organized crime and traffic offences. Although caveats remain, results indicate that the whole-of-government approach has a causal effect on the criminal involvement of OMCG and support club members, but that the nature of this effect depends on the type of crime and the subsample in question. Overall crime in the total sample seems unaffected by the approach, whereas organized crime committed by OMCG members is shown to decrease. We discuss whether the patterns observed are due to behavioural changes in OMCG and support club members, or whether they result from changes in police practices and, consequently, a changing dark figure of crime. We conclude our article with some reflections on future research.