Cell Site Analysis is a technique used to determine which cells a mobile telephone connected to given the features and behaviour of the mobile network at a particular geographical point or region of interest. A cell site expert can correlate this information to the Call Data Records provided by the mobile networks to determine possible locations of a mobile phone at the time of past connections. The geographical area that a cell covers is determined by a combination of factors including the cell type, cell orientation, transmission power, the arrangement of other cells, network usage and the physical features of the locality. These cell characteristics are variable over time and therefore must be considered as part of cell site analysis. Using specialist surveying equipment, the police can conduct Radio Frequency Propagation Surveys (RFPS), taking static readings inside or outside a location of interest or conducting ‘drive’ surveys. We can review this data, ensuring your client’s version of events is properly considered in any interpretation of these surveys.
Cell Site Analysis, however, goes beyond surveys alone. Interpretation of the Call Data Records is not a straightforward matter, with often complex rules required to properly attribute activity to a specific time, especially in relation to ‘data sessions’ rather than traditional calls and texts. In some cases, co-location analysis (establishing when two phones may have been together to infer attribution of that phone) is a critical part of the evidence, but perhaps even more important is to consider ‘non co-location’ to show when the phones may have been apart (inferring that someone else may have control).
Police forces often use intelligence analysts to produce cell site mapping as statements of fact. Due to the complexity of mobile phone networks, however, these facts may not tell the whole story, and the case of R v Calland makes it clear that an expert is required when performing analysis. For example, the Prosecution usually seek to demonstrate the cell site usage is consistent with their case, but this is rarely to the exclusion of other possibilities. It is important to consider the defendant’s account of their movements against the cell usage to assess which account, if either, is more likely given the cell site usage pattern. We aim to provide easy to use mapping, an interpretation of the evidence and, more importantly, what it means for your case.
If you would like to discuss a case involving cell site analysis evidence, you can talk directly our experts at our Durham office on 0191 332 4999 or email kbc@keithborer.co.uk.
