The effects of CCTV in reducing crime
Closed-circuit television (CCTV) is the use of video cameras to transmit a signal to a specific place, on a limited set of monitors often used for surveillance in areas that may need monitoring such as banks, casinos, airports, military installations, and convenience stores. 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 (public housing, car parks, public transport, other settings). Studies that investigated the effects of CCTV on crime were included.
Future CCTV schemes should employ high-quality evaluation designs with long follow-up periods and should pay attention to the methodological rigor of the evaluation designs. The use of a reasonably comparable control group by all of the 44 included evaluations went some way towards ruling out some of the major threats to internal validity, such as selection, maturation, history, and instrumentation. Exactly what the optimal circumstances are for effective use of CCTV schemes is not entirely clear at present, and this needs to be established by future evaluation research. But it is important to note that the success of the CCTV schemes in car parks was mostly limited to a reduction in vehicle crimes (the only crime type measured in 5 of the 6 schemes) and camera coverage was high for those evaluations that reported on it. In the national British evalua-tion of the effectiveness of CCTV, it was found that effectiveness was signifi-cantly correlated with the degree of coverage of the CCTV cameras, which was greatest in car parks. Furthermore, all 6 car park schemes included other in-terventions, such as improved lighting and security guards. It is plausible to EUCPN Summaries of Systematic Reviews3suggest that CCTV schemes with high coverage and other interventions and targeted on vehicle crimes are effective. Conversely, the evaluations of CCTV schemes in city and town centers and public housing measured a much larger range of crime types and only a small number of studies included other inter-ventions. These CCTV schemes, as well as those focused on public transport, did not have a significant effect on crime. Ideally, time series designs are needed with a long series of crime rates in experimental and control condi-tions before and after the introduction of CCTV. Future experiments are needed that attempt to disentangle elements of effective programs. Also, future experiments need to measure the intensity of the CCTV dose and the dose-response relationship, and need to include alternative methods of measuring crime (surveys as well as police records), for example using emer-gency department records. In order to investigate displacement of crime and diffusion of crime preven-tion benefits, the minimum design should involve one experimental area, one adjacent area, and one nonadjacent comparable control area. If crime de-creased in the experimental area, increased in the adjacent area, and stayed constant in the control area, this might be evidence of displacement. If crime decreased in the experimental and adjacent areas and stayed constant or in-creased in the control area, this might be evidence of diffusion of benefits. Unfortunately, few CCTV studies used this minimum design. Instead, most had an adjacent control area and the remainder of the city as another (noncompa-rable) control area. Because of this, any conclusions about displacement or diffusion effects of CCTV seem premature at this point in time.