Cross-border patterns in DNA matches between the Netherlands and Belgium

In this article we present the results of a study to explore if cross-border DNA matches between the Netherlands and Belgium are relatively more likely to occur in areas near the Dutch-Belgian border than in areas at some distance from this border. For this study we used the results of the transnational DNA profile exchange and comparison between the Belgian and Dutch DNA databases, which first took place in 2014. It appears that the Dutch regions adjacent to Belgium, i.e., Zeeland-West-Brabant, Oost-Brabant and Limburg, have relatively more DNA matches with Belgium than the other Dutch regions. In other words, a DNA profile obtained from a crime scene close to the Dutch border with Belgium is more likely to match with the profile of a person whose DNA profile is stored in the Belgian database than a DNA profile that originates from a crime scene further afield. Our data suggest that crimes committed by repeat offenders show a spatial pattern despite the presence of a national border, with crime scenes clustering in relatively close proximity to each other. The results of this study provide a better understanding of geographical patterns of cross-border criminal mobility.