New research shows that targeting each crime 'hot spot' in a city with 21 extra minutes of daily foot patrolling by Police Community Support Officers (PCSOs) could save the justice system hundreds of thousands of pounds through prevented crime.
Working with Cambridgeshire Constabulary to conduct a year-long experiment in Peterborough, researchers from the Institute of Criminology at the University of Cambridge randomly allocated 34 crime-prone areas to get 21 minutes of extra PCSO patrols a day.
They compared offences before and after the experiment between 38 hot spots with no increased patrol and the 34 with the increase using the Cambridge Crime Harm Index: a new tool that measures "harm caused to victims" by modelling severities in sentencing for different offences, rather than just totting up overall crime figures.
The research team calculated that targeted patrol time equal to two full-time PCSOs would prevent 86 assaults a year, or incidents of the equivalent crime 'harm value', saving potential costs to the public of eight years of imprisonment.
The findings, published in the Journal of Experimental Criminology, suggest that every £10 spent on targeted foot patrols prevents a further £56 in prison costs - a five-to-one return on investment.
While modern policing is characterised by a "reactive, fire-brigade" approach, usually vehicle-based, the researchers say their evidence strengthens support for the historic "bobbies on the beat" mode of policing focused on crime-prone areas.
"By working with us to conduct this experiment, Cambridgeshire Constabulary has set the standard for cost-effectiveness in policing," said study co-author Professor Lawrence Sherman, Director of the Cambridge Institute of Criminology and its Jerry Lee Centre for Experimental Criminology.
"Any other investment in policing can now be challenged to match the benefits of foot patrols in preventing the equivalent of either 86 assaults, or six burglaries, or six sexual crimes."
'Hot spots' are small urban areas, streets or intersections, where there is a concentration of crime - usually offences such as theft, burglary, violence and criminal damage.
During the experiment, 72 of Peterborough's 'hottest' hot spots randomly received either standard patrols (the control) or an average extra 21 minutes PCSO foot patrol per day (the treatment) over the course of a year.
In the 'treated' hot spots, these additional patrols - combined with vehicle patrols by Police Constables (PCs) these areas already received - amounted to an average increase of 56% in daily patrol time. GPS devices embedded in the radios of both PCs and PCSOs were used to track time spent in each location, a precise measure of the "treatment dosage" of police presence.
The researchers found that, on average per hot spot, 39% fewer crime incidents were reported by victims and 20% fewer 999 emergency calls to the police occurred in the 34 treated hot spots compared with the 38 control hot spots.
The extra 21 minutes of PCSO time per day for each of the hot spots amounts to 3,094 hours across all treatment areas, roughly equivalent to two fulltime PCSOs - no more than £50,000 on current salaries.
The Cambridge Crime Harm Index analysis suggests that, across all 34 treated hot spots, the equivalent of these two extra officers prevented crime amounting to 2,914 days - around eight years - of imprisonment, at a potential cost to the public of £280,000 under English sentencing guidelines.
"The use of the Cambridge Crime Harm Index and the Peterborough cost-effectiveness results provides a like-for-like metric to challenge those who demand more PC or PCSO time in patrolling schools, low-crime neighbourhoods, or traffic accident hot spots." Sherman said.
"This study should give both Police and Crime Commissioners and Chief Constables a benchmark for evaluating any other uses of police time other than hot spots patrols."
PCSOs are civilian members of police staff, used to bolster police presence and support PCs. They have no power of arrest, and cannot investigate crimes, but have specific powers to deal with minor public order offices - what's known as "soft policing".
Budgetary constraints in British policing mean PCSOs are the only officers who now conduct proactive and visible foot patrols. During the experiment, the PCSOs were told to concentrate on being visible to the exclusion of any other task.
The researchers' experimental evidence showed that every additional PCSO visit per day to the treatment hot spots decreased calls for service by approximately 34, with the number of crimes declining by around four.
"The experiment suggests that the number of visits to each hot spot may matter more than the total minutes - as if each time the police arrive they renew their deterrent effect on crime," said Dr Barak Ariel of the Lee Centre of Experimental Criminology, who was lead researcher on the Peterborough experiment.
Sherman says the latest results show that, if deployed tactically and proactively, 'soft' policing can achieve comparable crime reductions to the 'hard' threat of immediate physical arrest.
"These findings suggest that the probability of encountering an officer is more important than the powers that officer has, and that the frequency and duration of proactive patrolling deserves far more attention," said Sherman.
"More experiments like this one can produce an even more general estimate of the value of foot patrol activity, to make that value the 'gold standard to beat' in selecting cost-effective policing strategies," he added.
Professor Lorraine Mazerolle of the University of Queensland and Editor of the Journal of Experimental Criminology said that the Peterborough experiment showed "The deterrent role of police and PCSOs patrolling crime-harm hotspots is now indisputable: the police can, and do, prevent crime, they just need to be appropriately deployed to crime-harm hotspots."
Cambridgeshire Constabulary's Assistant Chief Constable Mark Hopkins said: "We're pleased to have worked with the Cambridge Institute of Criminology to conduct this research and we welcome the outcomes.
"We're keen to look at the findings in further detail and explore how they could help to influence our future policing plan."