UCL in the News: Sin cities: The geometry of crime

Mark Buchanan, 'New Scientist' Why does crime occur where it does? If you thought getting an answer to that question would mean getting inside the mind of the criminal, then you haven't met Kate Bowers.

She is less interested in the psychology of criminality than in the mathematics of crime itself, and is convinced that this can shed light on patterns of crime. Take burglary at people's homes. Although the pattern of burglaries in a neighbourhood may appear random, Bowers and her colleagues at the UCL Jill Dando Institute of Crime Science have found through computer simulations that burglaries actually spread in a predictable way, similar to a contagious disease. …

Bowers believes crime often has less to do with deviant psychology than with utterly mundane human habits and the physical environment in which potential criminals find themselves. In her view, crime is a normal, if undesirable, outcome of ordinary social interactions. …

Finding solutions to crime is much easier once a trend has been identified, and now mathematically minded criminologists say that computer models based on routine activity theory have the potential to make sense of a far more complex mix of social and physical factors that may influence crime.

One of the earliest studies using this approach was led by Michael Batty of UCL. Since its inception in 1964, the Notting Hill carnival in London has grown to attract more than a million visitors each year. …

After three people were murdered at the event in 2000, the Greater London Authority commissioned a review of public safety and asked Batty to create a computer model of people's movements in an attempt to identify better crowd-management strategies. …

Enlightened carnival organisers adopted the straighter route suggested by the computer analysis, and subsequent carnivals registered a big drop in both maximum crowd densities and the number of crimes committed.

Bowers's finding that burglaries spread like communicable diseases is another example of the power of computer modelling. It first emerged from work with her colleague Shane Johnson, completed four years ago. …

This revealed that, following a given burglary, the likelihood of another was increased for the next two weeks for any house within about 200 metres, though the probability tailed off at greater distances and after that time had elapsed. This pattern of communicability of crime strongly mirrors the patterns that epidemiologists find with diseases that spread from one person to another. …

To find out whether this trend was unique to the UK, last year Bowers and an international team of criminologists extended the study. …

Their computer model considers each recent burglary as a potential source of "infection" for future crimes. They can then estimate the likelihood of a subsequent crime in any given location by combining the risk associated with each of the previous burglaries - with those nearest making the strongest contributions. …

Taking a different approach to tackling urban crime patterns, Bill Hillier at UCL is mapping the physical environment in which crimes occur, and has developed a way of seeing cities that he calls "space syntax". …

In several studies, Hillier's group has shown how a detailed consideration of space and its influence on people can explain a lot of human interactions, including crime.

Over the past three years, he and his colleagues have been exploring how residential burglaries and street robberies in London link to other factors, such as geometrical features of the road network and the architectural properties of buildings. …

Hillier's as-yet unpublished findings could add an extra layer of information to the prospective crime hotspot maps that Bowers is working on. …