Mapping the DNA of the communication infrastructure: reconstructing where voice/data services may have been initiated or received  

by Ross Patel

The murders of Jessica Chapman and Holly Wells in Soham, Cambridge, in August of 2002, became one of the most high profi le criminal cases to be reported and documented in the last decade. Whilst the case is well known, what has not been widely appreciated is how specialist telecommunication evidence played a critical part in the investigation and ultimately helped to convict Mr Ian Huntley of the double murder.

Cell site analysis is a specialist branch of telecommunication evidence and is regarded as a maturing technical field. The practice that aims to determine the geographical location of a mobile phone through forensic analysis of the handset memory and assessment of complex technical data from the Communications Service Provider (CSP, such as T-Mobile or 02 Telefónica). Through careful assessment, taking into account the local topology (i.e. man-made or natural obstructions) as well as an appreciation of the transceivers that provided voice/data services to a subscriber and the radio frequency signal strengths, it is possible for specialist expert witnesses to triangulate the relative position or movement of a specific communication device. 

With over seventy-five million mobile phones presently active in the United Kingdom, which is more devices than there are people, combined with the fact that telephones are used for both social and business purposes it is no wonder that cell site analysis is an increasingly important technique used in lawful investigations.

Mobile telephones in the United Kingdom are primarily based upon the ‘Global System for Mobile Communications’ (GSM) protocol. GSM uses a digital link technology whereby multiple phones share a radio frequency channel by taking turns – using the channel exclusively for an allocated time slice then releasing it and waiting briefl y while other phones use it. Mobile telephone handsets communicate with the service network via masts, or ‘cell sites’.

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