Cell site analysis is a technique to determine the general geographical location of a mobile telephone at the time of its past connections. The geographical landscape of the UK and Ireland is scattered with mobile telephone masts which mount cells which a telephone connects to. In simple terms, when a mobile telephone is making/receiving a call or a text message it uses a cell to coordinate the connection. Each cell has a unique number assigned to it known as the Cell ID. It is this unique cell number that the network providers store for each connection a telephone makes and receives on their network.
The records containing the cell information are known as the Call Data (Detail) Records (CDRs for short). It is these CDRs that allow cell site analysis to be conducted. SRC is able to provide a free overview and advice for your case evidence to determine the best way to progress given your case scenario and advise you how to obtain the required records from the CPS/police or directly from the network providers. Contact SRC for provision of this service.Coverage of Cells
Each cell has a geographical area in which it may be used to make a call or text. However, the coverage of a cell is determined by many factors including its orientation, the physical landscape surrounding it, if the cell and those surrounding are functioning correctly etc. Additionally, just like how your radio signal sometimes can be intermittent, the mobile signal from a particular cell in a given location is also variable due to physical changes in the landscape/local area, changes in the positioning and configuration of cells, weather and network usage.
Sam Raincock is principal scientist and an expert witness at SRC and has also found large differences in the signal strength provided by a cell depending on whether a mobile telephone is located inside or outside a building including large difference sometimes being noted between rooms inside a building. Hence, she often conducts her cell site analysis to replicate the scenario including taking readings in all of the rooms of a building, taking the readings at approximately the same time as the past calls and taking the readings for as long as possible to obtain a better indication of the signal strength variability being detected. What are the limitations?
Cell site analysis is useful in enabling an expert to state that a telephone was travelling over large distances (for example, a telephone moving from the London area to the Manchester area), however, for short distances or static locations things become more variable and uncertain.
When cases involve a telephone being located in a fairly small geographical area (in the order of less than 5 miles), usually cell site analysis is conducted to answer questions about a particular scenario. Typically, it will be used to address if a telephone could have been located at the scene of an alleged crime scene and/or where the defendant states they were located. In such a situation, an expert is likely to conduct network signal testing of the mobile network at both locations. It can also determine the coverage of cells which can sometimes turn up surprises.Instructing SRC in Cell Site Analysis cases
SRC specialises in large and complex cell site analysis cases particularly involving multiple locations, drive testing interpretations (when network readings are obtained via driving around the general area in a vehicle) and cases where the congregation of telephones in certain areas is significant.
In previous cases, Sam's analysis has resulted in experts revising their statements, provision of joint statements of agreement, evidence being withdrawn and disproving a case scenario via the demonstration of contrary information.
SRC has also developed various software which can be used to process comparisons between multiple telephones to determine inconsistencies and consistencies in their locations of use when comparing for general use and attribution. SRC can also provide full assessments of telecoms evidence with respect to attribution.
Sam is an experienced cell site analysis expert working on a range of case in the UK and Ireland including: