Friday, 18 June 2010

The fingerprint of where and when a burglary is committed

In the land of fiction, it's the criminal's modus operandi - his method of entry, his taste for certain jewellery and so forth - that can be used by detectives to identify his handiwork. The reality according to a new analysis of solved burglaries in the Northamptonshire region of England is that these aspects of criminal behaviour are on their own unreliable as identifying markers, most likely because they are dictated by circumstances rather than the criminal's taste and style. However, the geographical spread and timing of a burglar's crimes are distinctive, and could help with police investigations.

Lucy Markson and colleagues analysed 160 burglaries committed in Northamptonshire between 2006 and 2008 by 80 male serial offenders. Each burglar had committed two of the crimes. Markson jumbled up the burglaries and looked to see if two crimes committed by the same offender - so-called 'linked crimes' - were more similar, on average, on a range of factors, than two crimes committed by two different offenders.

Each burglary was analysed according to its timing, geographical location, and over 79 aspects of modus operandi behaviour categorised together under three domains: 'entry behavior', 'target selection', and 'property stolen'. Comparing crimes across each of these domains one at a time failed to distinguish between linked and unlinked crimes. Only when all three domains of modus operandi behaviour were considered together were burglaries by the same man distinguished from those by two different men (but still only with an accuracy of 58 per cent).

The key finding is that even more effective as a distinguishing factor than all three domains of modus operandi behaviour combined was geographical location. That is, two burglaries within Northamptonshire committed by the same man tended to be closer together geographically than two burglaries committed by two different men. Timing was another useful factor - two crimes by the same burglar tended to happen closer together in time (measured in days) than unlinked burglaries. Combining timing and spatial distance correctly identified 86 per cent of burglary pairs as either linked or unlinked.

Another pattern the researchers looked for was whether modus operandi behaviours are more similar between two crimes occurring closer together in time, but no such pattern was observed.

Timing and spatial distance have been identified as useful markers of linked crimes before but only ever in metropolitan areas, so this is the first demonstration in a more rural, sparsely populated context. 'The current study has shown that offenders do exhibit a degree of consistency and distinctiveness across certain crime behaviours but that not all offence behaviour can be used to accurately distinguish between burglaries committed by the same and different offenders,' the researchers concluded.

ResearchBlogging.orgMarkson, L., Woodhams, J., & Bond, J. (2010). Linking serial residential burglary: comparing the utility of modus operandi behaviours, geographical proximity, and temporal proximity. Journal of Investigative Psychology and Offender Profiling DOI: 10.1002/jip.120

Post written by Christian Jarrett (@psych_writer) for the BPS Research Digest.

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