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Evidence and CCTVs: A slight return

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This morning, in a relatively brief post, I commented on the illusion of security provided by closed-circuit TV (CCTVs) cameras, the proliferation of these surveillance devices in Toronto's downtown core in the lead up to the G20, and the promise by Toronto police to remove the cameras after the summit.

A friend of mine who works in privacy and security thought I should provide more evidence on how CCTVs do very little other than chip away at privacy and civil liberties. I agree with him. Here's some additional evidence, hopefully buttressing my previous argument.

A breach of civil liberties and privacy

Germany's Constitutional Court has stated that "the knowledge of being under surveillance, why and by whom is crucial for a democratic society and the autonomy of its citizens" (Töpfer, Hempel and Cameron, 2003, p. 6).

Denmark has a legal presumption against surveillance of public spaces by private entities, while police use of photographic surveillance is heavily regulated (Norris, McCahill and Wood, 2004, p. 121).

The Supreme Court of Canada has stated that to "permit unrestricted video surveillance by agents of the state would seriously diminish the degree of privacy we can reasonably expect to enjoy in a free society" (Deisman, 2003, p. 18).

This 1990 SCC ruling prompted the former Privacy Commissioner of Canada to note that continuous and indiscriminate monitoring not based on probable cause is a breach of Charter rights as well as the United Nation's Universal Declaration of Human Rights, and the International Covenant of Civil and Political Rights (Deisman, 2003, p. 18).

Where constitutional protections of privacy are weak or where human rights are routinely disrespected, one usually finds greater use of CCTVs in public spaces.

Ineffective crime deterrent, poor face recognition and not a useful tool for prosecutors

Rather than prevent crime or enhance security, CCTVs have a symbolic value - one that attempts to provide the illusion that governments are addressing crime (or ensuring safety). According to Winge and Knutson (2003), the Oslo police force had high hopes for CCTVs, but following an evaluation of the surveillance devices there was no evidence of a great reduction in criminal behaviour, increased public order, or enhanced feelings of safety (p. 138).

With respect to using CCTV footage as evidence, I said in my previous post that footage has been helpful in recording criminal acts or helping law enforcement and courts understand the setting of an act, but my statement should not go unchallenged.

Lee et al (2009) cite a number of studies indicating that most people fare poorly when attempting to match unfamiliar faces to photographs from high and low quality video (p. 25). As for those who are trained in facial recognition, they seem to do better than the general public with higher quality video, but experience the same number of errors as the public with low quality footage. More study on analysis by trained experts is needed.

Further, Davis and Valentine (2009) observe that even in optimal conditions, matching the identity of a person in a video is highly susceptible to error.

Finally, in a study prepared by the American Civil Liberties Union (2007), it is found that CCTVs do not have a significant impact on the number of crimes solved and that law enforcement overestimates the use of CCTV footage to convict criminals. A spokesperson for the Maryland state attorney's office said that the office has not "found [CCTVs] to be a useful tool to prosecutors...they're good for circumstantial evidence, but it definitely isn't evidence we find useful to convict somebody of a crime...We have not used any footage to resolve a violent-crime case" (p. 13)

Promising the appearance of security

Norris et al (2003) offer a fine summary of the symbolic use of CCTVs:

"The extent to which such measures [widespread introduction of CCTVs] do anything to protect from further tragedies is questionable, but largely irrelevant. For politicians, there is a need to be seen to be doing something. And as the psychological, social or political conditions that give rise to such incidents are complex, and possibly intractable, technological fixes which promise the appearance, if not the reality of security are highly appealing." (p. 126)


Davis, J.P. and Valentine, T. (2009). CCTV on trial: Matching video images with the defendant in the dock. Applied Cognitive Psychology, 23, 482-505.

Deisman, W. (2003) CCTV Literature Review and Bibliography. Research and Evaluation Branch, Community, Contract and Aboriginal Policing Services Directorate, Royal Canadian Mounted Police. Ottawa.

Lee, W-J., Wilkinson, C., Memon, A., and Houston, K. (2009). Matching unfamiliar faces from poor quality closed-circuit television (CCTV) footage: An evaluation of the effect on training on facial identification ability. AXIS, 1(1), 19-28.

Norris, C., McCahill, M. and Wood, D. (2004). Editorial. The growth of CCTV: A global perspective on the international diffusion of video surveillance in publicly accessible space. Surveillance and Society, 2(2/3), 110-135.

Schlosberg, M. and Ozer, N. A. (2007). Under the watchful eye: The proliferation of video surveillance systems in California. ACLU of Northern California. http://aclunc.org/docs/criminal_justice/police_practices/under_the_watch...

Töpfer, E., Hempel, L. and Cameron, H. (2003) Watching the Bear: Networks and islands of visual surveillance in Berlin. Urbaneye Working Paper no. 8. Centre for Technology and Society, Technical University of Berlin.

Winge, S. and J. Knutsson (2003) "An Evaluation of the CCTV Scheme at Oslo Central Railway Station." In M. Gill (ed.) CCTV, Leicester: Perpetuity Press.

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