Novel insights into offenders’ activity spaces

It is well established that offenders commit most crimes near their routine activity space: the locations where they engage in their daily activities. However, research examining the geography of offenders’ routine activity spaces has largely been limited to a few core locations such as homes, prior homes, the homes of relatives and prior offense locations. It has also been limited to small study areas, such as single cities. Due to these gaps in available data, our knowledge of offenders’ activity spaces has remained sparse.

Comprehensive dataset from the New Zealand police

In their recent paper A national examination of the spatial extent and similarity of offenders’ activity spaces using police data, Sophie Curtis-Ham, Wim Bernasco and co-authors Oleg Medvedev and Devon Polaschek provide novel insights into offenders’ activity spaces. Using a comprehensive dataset from the New Zealand police, they assess the sizes of individual offenders’ activity spaces, and establish how these activity spaces overlap with those of other offenders. In addition to homes, prior homes, relatives’ homes and prior crimes, the New Zealand police data contain a much wider set of activity locations. It also includes schools and workplaces, locations of crimes where individuals have been victims or witnesses, locations of other police-registered incidents in which the individuals have been involved (e.g. domestic disputes, drunk or disorderly behavior), and miscellaneous encounters or sightings registered by police for operational or investigative purposes, labelled, for example, as ‘spoken to at’, ‘seen at’, ‘frequents’ or ‘arrested at’.

Whereabouts of offenders much more completely investigated

Another feature of the study is that it is not restricted to a single city or region but broadens the geographical scale to the national level of New Zealand, which allows the authors to investigate the whereabouts of offenders much more completely than previous studies did.
Using information on 60,229 burglary, robbery, and extra-familial sex offenders in New Zealand, a wide range of activity locations were reported for most burglary and robbery offenders. Fewer were reported for sex offenders, reflecting their sparser histories of police contact.

Most offenders share large parts of their activity spaces with other offenders

The activity spaces of many offenders span wide geographic distances, including multiple cities across the country, even within relatively short time frames. This finding might reflect a distinct feature of mobility patterns in New Zealand, but also suggests that prior studies may have underestimated offender mobility by limiting the sample to single cities or urban areas. Most offenders share large parts of their activity spaces with other offenders, and those who offend in the same or in nearby locations, in particular if they are co-offenders, have more activity space in common than those who offend further apart.

Geographically prioritized suspect search

The size and similarity of offenders’ activity space is relevant for geographic offender profiling, an investigative technique intended to help the police to geographically prioritize suspect searches. The overlap of offender activity spaces is a challenge for geographic offender profiling, as it indicates that offenders’ activity spaces are not very distinctive. Similarly, the large size of offender activity space further complicates geographic offender profiling, because it means that the pool of possible suspects is also large.

Publication details and further reading

Curtis-Ham, S., Bernasco, W., Medvedev, O.N., & Polaschek, D. (2021). A national examination of the spatial extent and similarity of offenders’ activity spaces using police data. International Journal of Geo-Information 10, 47.