Prospective crime mapping in operational context Final report

To recapitulate and elaborate, the approach taken may be summarised as shown below:1. The burglary data were sorted in date order.2. For each period of time (before and during the pilot), the previous week’s events were used asa historic buffer period to allow all events that occurred within seven days of another to beidentified.3. Each burglary event was then considered in sequential order.a. For the first event considered, only the historic data were searched to see if earlierburglaries occurred within the critical thresholds of the first event; where they did theywere added to the series for that reference event.b. For the second event considered, all of the historic data (including the first referenceevent) were searched, and events that belonged to a series identified as per step a.c. Once all crimes had been considered, for every event it was possible to calculate themaximum length of the chain for which that event was the terminal event and howmany chains of every length were identified.Using this approach, it was possible to answer the question, ‘when a burglary occurs how manycrimes previously occurred nearby in space and time?’ It is, of course, possible that any cluster soidentified could be part of a longer cluster which included events that subsequently occurred.Expressed a slightly different way, clusters identified in this way may overlap with one another withone cluster including some events of another – although for any particular series length no twoclusters would include exactly the same events – there would be at least one different crime in thelonger chain (the shorter being a subset of the other).Having summarised the data in this way, it was possible to calculate what proportion of burglarieswere the terminal event for different lengths of space-time series. The results, shown as Figure A3.4,illustrate that around one-third of events occurred within 400m and one week of at least oneantecedent both before and during the pilot. Around 15 per cent of events occurred nearby and withinone-week of at least two others. For the two intervals of time considered, the longest series identifiedconsisted of 12 burglaries that occurred close to each other in both space and time. Before discussingthe differences for the two periods of time, it is important to note the implication of this finding, which isthat it clearly illustrates the flux of crime. If burglaries occurred in the same places all the time, eitherconsiderably longer series would have been identified, or a higher proportion of events would belongto longer series. This emphasises the need for a dynamic predictive capability for the deployment ofcrime reductive resources. Simply targeting the same areas over time is unlikely to direct resources tothe right places at the right times.92