Effects of Closed Circuit Television Surveillance on Crime

摘要

This Campbell systematic review examines the effects of closed circuit television (CCTV) on property crime and violent crime. The review reports on whether using CCTV results in crime displacement, and also assesses whether using CCTV leads to the spread of crime prevention benefits. The authors found 44 evaluations. The studies were from the United Kingdom, the United States of America, Canada, Norway and Sweden. Most of the studies (34) were from the United Kingdom. CCTV has a modest impact on crime. Effectiveness varies across settings. Surveillance is more effective at preventing crime in car parks, and less effective in city and town centers, public housing, and public transport. CCTV appears most effective in car parks at reducing vehicle crimes such as thefts from cars or stealing cars. The effectiveness of CCTV surveillance is greater when camera coverage of an area is high. CCTV surveillance does not have an effect on levels of violent crime. In all six of the CCTV car park studies, CCTV surveillance was an element in a broader package of crime prevention measures, such as extra security guards, better lighting, and fencing. It is not possible to assess the independent effects of each of these different components. The available evidence does not allow a conclusion as to whether CCTV leads to a displacement of crime or a diffusion of crime prevention benefits to other areas. Abstract Background In recent years, there has been a marked and sustained growth in the use of CCTV to prevent crime in public space in the U.K., United States, and other Western nations. In the U.K., CCTV is the single most heavily funded crime prevention measure operating outside of the criminal justice system. A key issue is how far funding for CCTV has been based on high quality scientific evidence demonstrating its efficacy in preventing crime. There is concern that this funding has been based partly on a handful of apparently successful schemes that were usually evaluated with less than rigorous designs, done with varying degrees of competence, and done with varying degrees of professional independence from government. Recent reviews that have examined the effectiveness of CCTV against crime have also noted the need for high quality, independent evaluation research. Objectives The main objective of this review is to assess the available research evidence on the effects of CCTV surveillance cameras on crime in public space. In addition to assessing the overall impact of CCTV on crime, this review will also investigate in which settings, against which crimes, and under what conditions it is most effective. Search strategy Four search strategies were employed to identify studies meeting the criteria for inclusion in this review: (1) searches of electronic bibliographic databases; (2) searches of literature reviews on the effectiveness of CCTV in preventing crime; (3) searches of bibliographies of CCTV studies; and (4) contacts with leading researchers. Both published and unpublished reports were considered in the searches. Searches were international in scope and were not limited to the English language. Selection criteria Studies that investigated the effects of CCTV on crime were included. For studies involving one or more other interventions, only those studies in which CCTV was the main intervention were included. Studies were included if they had, at a minimum, an evaluation design that involved before‐and‐after measures of crime in experimental and control areas. There needed to be at least one experimental area and one reasonably comparable control area. Data collection & analysis Narrative findings are reported for the 44 studies included in this review. A meta‐analysis of 41 of these 44 studies was carried out; the requisite crime data was missing in other 3 studies. The “relative effect size” or RES (which can be interpreted as an incident rate ratio) was used to measure effect size. Results are reported for total crime and, where possible, property and violent crime categories using (mostly) official data. In the case of studies that measure the impact of CCTV programs on crime at multiple points in time, similar time periods before and after are compared (as far as possible). The review also reports on displacement of crime and diffusion of crime prevention benefits. Main results The studies included in this systematic review indicate that CCTV has a modest but significant desirable effect on crime, is most effective in reducing crime in car parks, is most effective when targeted at vehicle crimes (largely a function of the successful car park schemes), and is more effective in reducing crime in the U.K. than in other countries. Reviewers’ conclusions We conclude that CCTV surveillance should continue to be used to prevent crime in public space, but that it be more narrowly targeted than its present use would indicate. Future CCTV schemes should employ high‐quality evaluation designs with long follow‐up periods.