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Institute of Criminology

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Two new experiments undertaken by Cambridge University MSt in Applied Criminology and Police Management students found major reductions in violent crime on days when police conducted just one 15-minute foot patrol. Both studies were done independently under Cambridge academics’ guidance by police in Southend, Essex and across Bedfordshire, completing over a total of 3,690 days of measurements of crime and patrol in a total of 41 hot spots. The twin experiments, led by two senior leadership apprentices from the Institute of Criminology's MSt in Applied Criminology and Police Management degree course, both found that a single 15-minute patrol reduced all serious violence for an entire 24 hour period. On days with foot patrols, the crime harm severity scores were 44% to 88% lower than on days in which no patrol was provided. Whether a location received a patrol was decided daily by computerized random assignment.

The findings have just been published as two separate articles in the Cambridge Journal of Evidence-Based Policing:

The success of this research in Southend, Essex has also been reported on by the BBC: Hotspot policing cuts Southend crime by 74%, says Essex force

The Essex trial was led as a master’s thesis by Chief Inspector Lewis Basford; the Bedfordshire trial was led as a master’s thesis by Michelle Leggetter, with support from Assistant Chief Constable Jacqueline Sebire. 

Professor Lawrence Sherman, Director of the Cambridge Police Executive Programme (MSt in Applied Criminology and Police Management) course, said that ‘’These trials are the strongest UK evidence yet that foot patrols in the right places can cut violent crime.”  The trials made no attempt to measure effects of specific patrol tactics, such as stop & search. They focused instead on whether police were visibly present on foot patrols. Both trials were funded by Home Office special funding for police forces with greatest challenges from serious violence.  The studies used similar methods, but differed greatly in the size of the hot spots they targeted. The Essex trial used 20 hot spots of 150 metres squared; the Bedfordshire trial used 21 hot spots of two kilometres squared. They also differed in the proportion of days assigned to patrol that actually received patrol: 98% in Essex and 68% in Bedfordshire. 

Dr Matthew Bland, a Cambridge University criminology lecturer who analyzed the Bedfordshire experiment, said that it found ‘’strong evidence of cumulative effect of patrolling every day, rather than less frequently.”  Because the number of days of consecutive patrolling was also randomly assigned, Bland was able to compare just one day to up to four days in a row, and reported that, “by the fourth consecutive day of assigned foot patrols, the average crime harm severity in the hot spots dropped by over 99%. Since that drop caused no clear increase in crime in other places nearby, we can interpret it as a finding of cumulative deterrence rather than displacement.” 

Both trials used minute-by-minute GPS tracking of the exact times of arrival and departure of the foot patrol officers in the targeted hot spots. While these measures were specially designed for the experiments, Professor Sherman said that ‘’they could readily be adopted for business as usual. The findings of these experiments might then help to re-shape priorities in the fight against serious violence. When police cars arrive hours--or even days—after being dispatched to the location of a low-seriousness crime, they are roundly criticized. Yet when hot spots of violence go for days without a single 15-minute foot patrol, no one raises an alarm. This new research suggests that police agencies themselves can raise an alarm, literally. They can use new technology to track patrols in hot spots 365 days a year—and build in ‘digital alarms’ to send out a foot patrol urgently when two or three days goes by without preventive patrols.’’

Both the numbers of crimes and the seriousness of them were reduced by the patrols. In Essex, serious crimes on days with no patrol were reported at the rate of 11 per year, but that rate dropped to 3 serious crimes per year for days on which the patrols were performed. In Bedford, with larger areas, the annualized number of serious violent crimes dropped from 55 on no-patrol days to 40 per year in days with a patrol assigned.

The studies both used the Cambridge Crime Harm Index to measure the seriousness of the crimes. This index multiplies the number of crimes in each category (such as robbery or murder) by the number of days of imprisonment recommended for that category by the Sentencing Council for England and Wales. It was by this metric that the Crime Harm Index scores for the patrol days in Essex were 88% lower than on days with no patrol, and 44% lower in Bedfordshire.  Assistant Chief Constable Jacqueline Sebire of the Bedfordshire Police said that “We have learned a great deal from our experiment, and are already putting its lessons into practice.” Dr. Sebire, who is also the National Police Chiefs’ Council lead for reducing serious violence, said that the Bedfordshire Police would soon launch a second experiment in refining hot spots patrols.

For further information contact: Professor Lawrence W. Sherman  Tel (+44) (0) 759 925 3770