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Digital Imaging Procedures Digital CCTV is increasingly becoming a surveillance approach of choice for many end users. Whist traditional analogue surveillance systems still lay an important role in many applications, there are times when such solutions cannot complete with the advanced functionality offered by the digital revolution. To ensure the admissibility of digital footage as evidence, the police scientific development branch has published guidelines for the use of digital images ass evidence. The digital imaging procedures (v1) state that CCTV should be regularly maintained and that an audit trail should be commenced at the earliest opportunity. With regard to the later point, an audit trail for digital CCTV is very much the same as one for an analogue system. However with digital systems the audit trial must also keep records of which copy is designated as a master copy and which is a working copy. Since digital images can be replicated with no derogation, and due to the fact the first storage medium is usually an integral part of the DVR (Digital Video Recorder). The document lays down the procedure for the creation of a master copy and a subsequent working copy for viewing and distribution to authorized parties. The master copy should be stored securely and kept in accordance with the evidential procedures. The master copy needs to be taken directly from the original recording medium and stored onto a removable medium. This removable medium must be a WORM-type device. WORM is an acronym for Write Once, Read Many. Once the Master copy is made, no further data can be added, and the data stored cannot be altered or changed in any way. WORM media includes CD-R, DVD-R and DVD+R products. A working copy can be produced simultaneously with the master copy or subsequently to the master copy from the original footage, or can be produces from the master copy. Media containing footage to be used as evidence should be clearly labeled, and should included the relevant image sequences, a text file stating an hardware or software requirements for replay, metadata such as time and date information bound to the footage, license free software for view and make copies of the footage including editable sequences ( the DVR manufacture should supply this) and instructions to copy the footage to VHS cassette plus details of any changes that may occur if the cassette is then played alongside the digital footage. You may also include- although there is currently no requirements to do so – a copy of the audit trial, a test sequence to ensure replay is correct and authentication or verification software. For more information please visit: http://www.crimereduction.gov.uk/cctvminisite23.htm
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