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Storing CCTV video material

The identification of the London bombers would have involved the review of CCTV video tapes from main line rail and Underground stations, public surveillance operations, and London businesses, particularly those around Westminster.

As of 23 July, there were an estimated 25 000 video tapes reportedly containing video data amounting up to hundreds of thousands of hours being reviewed by police. The speed of the police in obtaining, processing, and identifying the guilty parties was nothing short of phenomenal. This must have been one of the largest CCTV review exercises worldwide. It follows from the extensive review of public and business tapes that led to the arrest of the Brixton nail bomber where extensive reviews of CCTV footage led to clues that resulted in the final arrest of the person responsible.

There were a number of notable factors that would have been associated with the success of the exercise. The speed of retrieval of video information, whether in analog or digital format, was a key element in the success of the police exercise. This would have included follow ups with surrounding CCTV operations who were more than likely using different data formats and mediums for their video storage. For me, the ability to spot the perpetrators using very few clues as to their appearance and location was an example of viewing efficiency that many commercial operations would like to have. The processing speed to go through so much material would have been helped by careful organisation and establishing of priority areas but was nevertheless incredibly quick.

The key to success for the London bomber investigations was that video was available in storage and was accessible. Indeed, the Metropolitan police reportedly requested operations, including businesses, to ensure that video footage was stored safely and securely with full details. One of the foremost lessons for me in this is that a number of commercial operations in South Africa and elsewhere are likely to come out somewhat badly if requested to retrieve stored data. This could be due to a number of reasons:

* Where VCRs have been used, the storage media such as tapes have not been replaced on a regular basis. Some standards require tape replacements every 8 or 12 times they have been used. Continual use of the same tape eventually results in wearing of the magnetic media to the extent that eventually one is going to be looking at noise rather than video.

* Turnover in digital data - digital recording systems have been set so the retention of data is over a minimal period - in some cases from as little as 48 hours.

* Archiving facilities - there are no facilities to archive data. This is a particular problem with some digital systems. While often supplied with a CD or DVD writer, they can cope with archiving specific incidents, but to indefinitely archive a day or days of material is virtually impossible.

* Equipment failure - equipment breakdowns which are not repaired, or equipment not turned on can still be found.

Most operations are obviously not in the same situation as the police in the London bombing example. The urgency, availability, and response are all enhanced when such an event occurs. However, for any operation where the video is likely to be used for incident detection and taking action against offenders, the retention of data is still highly important. In the UK, for example, city and town centre operations are required to keep their data for at least 30 days. Even where there are not legal requirements or best practice expectations to keep data, 30 days seems a good benchmark. With DVR systems, this may mean you sacrifice some recording and enhance others in order to handle the storage demands of additional days.

Some examples of reasons for having to go back to data include:

* Live viewing is typically not the most efficient of processes. Video review usually increases the detection rates of an operation appreciably. This video needs to be accessible and available if such review is to happen.

* Committing a crime usually involves some knowledge of the place and conditions. Criminals will often stake out or review a potential crime scene prior to an incident occurring. If there are no clear suspects already identified, police in the UK frequently review tapes of who has been doing what at a crime location over the last couple of days in order to identify potential suspects. This principle works for anyone dealing with crime.

* Post investigation - in many cases in industry and commerce, a loss may only be detected some time after the event has occurred. In other cases, tipoffs or investigations may highlight that something needs to be looked at. If one goes back to the video source only to find that it has been deleted off the system or taped over, it means that your system is not providing any value for such cases.

* Legal queries - if you prosecute or hold a disciplinary hearing over a case using a specific section on incident material, the defence may request additional video footage of the material surrounding the incident in order to better understand the context of the incident material. If your incident material does not cover the whole time period sufficiently to get a clear understanding, the evidence can become less effective and subject to challenge. If a lawyer asks for a more comprehensive footage of the incident situation, what will you be able to provide two weeks to a month later?

* Alerts - other instances may alert you to conditions that require investigation - in an instance a few years back a syndicate was caught at one of the local casinos. A visiting operator from another casino remembered some of the characters and immediately initiated an investigation when it was established that some of the syndicate members had been there three days before.

If you find that you are wanting to retrieve data and it is no longer on your system, you know that you need to re-look at your storage strategy. Even the UK police may find that based on additional information that comes to light, they want to go back to material that may be a few weeks old, and that might just have the potential for an essential breakthrough.

Dr Craig Donald is a human factors specialist in security and CCTV. He is a director of Leaderware, which provides instruments for the selection of CCTV operators, X-ray screeners and other security personnel in major operations around the world. He also runs CCTV Surveillance Skills and Body Language, and Advanced Surveillance Body Language courses for CCTV operators, supervisors and managers internationally, and consults on CCTV management. He can be contacted on 011 787 7811 or [email protected]

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