This blog is a part of our series, "Perspectives in Crime" where we explore leading academic studies that touch on crime data.

The use of close-circuit television cameras (CCTV) for surveillance and protective purposes has been a topic of debate since the initial popularization of their use. Intended as a deterrent of crime, a facilitator of timely response, and as an investigative asset, their actual efficacy often comes into question, as well as criticism oriented around privacy concerns. Despite debate, limited research has empirically approached the question of CCTV usefulness.

The value of CCTV as evidence

A 2017 study by Matthew Ashby, a criminologist at University College London, entitled “The Value of CCTV Surveillance Cameras as an Investigative Tool: An Empirical Analysis” published in the European Journal of Criminal Policy Research, explores the degree to which CCTV recordings were useful to police during criminal investigations. Utilizing data from over 250,000 crimes recorded by the British Transport Police recorded on the British railway network over 5 years (2011-2015), Ashby analyzed the offenses and circumstances under which investigating authorities considered CCTV useful to investigations. Research found CCTV footage efficacy to vary by crime type, consistently useful in instances of robbery and assault while utilized less for drug offenses and crime types with more uncertain timeframes.

Most CCTV research has focused on their ability to prevent and deter crime by introducing continuous guardianship into an area, while less study has focused on the impact of CCTV on investigations after a crime has occurred. Ashby’s paper focused on the following questions: How often do CCTV cameras provide useful evidence in criminal investigations? How does this evidence vary by crime types? And in what circumstances is CCTV most likely to be useful to a criminal investigation?

Although some may hold that CCTV is only useful if it leads to a suspect being convicted, CCTV can also lead to a suspect being eliminated from an investigation or help determine if a crime has been falsely reported. Additionally, footage can help investigators to corroborate or refute witness testimony as well as locate additional witnesses.

The availability and use of CCTV footage in criminal investigations

The British Transport Police (BTP) have included questions on electronic forms filed by first-line supervisors at the end of each investigation, asking first if CCTV had been useful in the case, and if not, what had prevented CCTV from being useful.

In the five years studied, 251,195 crimes were recorded by the BTP, about 138 crimes each day. According to BTP filings, CCTV footage was not available or not requested for 54.7% of the reported incidents, and therefore offered no assistance to officers during their investigation. In 64.9% of cases where footage was available, investigators deemed it useful. Ashby’s findings note that prior studies reporting low usefulness of CCTV may be because of CCTV’s infrequent availability to investigators.

Figures 1 and 2 show the relationship between CCTV footage’s availability and utility:

Pie chart showing that CCTV is useful in 65% of investigations vs not useful in 35% of investigations
Pie chart showing that CCTV is not available for 55% of investigations, is available but not useful in 16% of investigations, and is useful in 29% of investigations

The utility and efficacy of CCTV footage varied widely by crime type. In instances of robbery, assaults, sexual offenses, CCTV footage was frequently available and consistently useful to investigators. Instances of theft from vehicles, burglary, fraud, and criminal damage often did not have available or useful CCTV footage. Crimes relating to drugs and weapons rarely listed available footage, but when footage was available it was almost always useful to investigators. During the study years, CCTV footage was useful in the investigation of 5,343 assaults, 1,365 personal robberies, and 2,810 sexual offenses.

Figure 2 shows the proportion of crimes where CCTV footage was available and useful to investigations.

Chart showing the breakdown of different crime types by what percent of the time they have useful CCTV footage or available CCTV footage

Available and useful CCTV evidence significantly increased the detection rate for all types of crimes except for drugs, fraud, and public order. The most significant change was for robbery, where the probability of detecting an offense increased to 55.7% from 8.9% without CCTV footage. For all types of acquisitive crime other than shop theft, useful CCTV evidence produced an increase in detection rates of 19% or greater. CCTV footage was associated with higher detection rates of all crime types except for weapons and drug offences, which are typically only associated with proactive policing tactics like ‘stop and search.’ Meaning that the discovery of an offense typically also provides the evidence necessary to solve it. These crimes are largely “self solving,” and CCTV footage offers little additional information to law enforcement.

Is CCTV useful in every case?

The type of crime, location of crime, passage of time, and severity of crime all drove whether police would seek CCTV footage and whether that footage would be of assistance in the course of an investigation.

If the aoristic window (the window of time in which a crime may have occurred) is too great, CCTV footage is unlikely to be of aid, as the amount of footage to be analyzed can quickly exceed the hours of labor necessary to study the footage. Similarly, if a crime is detected and solved very quickly, investigating officers are unlikely to retrieve CCTV footage if it is felt to be extraneous or unnecessary.

In analysis the placement of cameras bore a strong impact on the availability and usefulness of CCTV footage. While cameras are ubiquitous in train stations, there is significantly less coverage along tracks between stations. Fewer cameras also mean less overlap between the areas covered by each camera, whereas in a station multiple camera views may offer investigators a more comprehensive view of incidents.

CCTV as a meaningful tool

Ashby’s 2017 study highlighted the usefulness of CCTV footage in assisting law enforcement with investigations of most crime types. The research found that:

  • Most investigators noted the usefulness of the footage in investigating crime.
  • Footage significantly increased the likelihood of investigations being solved.
  • The usefulness of footage varied by crime type, with robbery and assault being the most impacted crime types.

This study offers empirical evidence to conversations regarding CCTV’s utility in criminal investigations and finds that though circumstances and location figure highly into the effects, CCTV surveillance can be a meaningful tool for criminal investigation.

Published March 21, 2022


Ashby, Matthew P.J. 2017. ‘‘The Value of CCTV Surveillance Cameras as an Investigative Tool: An Empirical Analysis.’’ Eur J Crim Policy Res 23:441-459.