Cell Site Analysis – The Number Crunching
The importance of cell site analysis cannot be underestimated. It frequently is presented as part of the prosecution case and naturally should be considered on the behalf of the defendant(s). It is more common now that the defence team initiate Cell Site Analysis even when the Crown does not rely on such evidence. Our own cell site experts are frequently asked what appears to be a standard set of questions during their evidence, but there is one form of questioning that has an ‘irritable inference’ which could be easily dismissed or potentially be catastrophic, regardless of whether it is a Crown of a Defence Expert report.
The cell site analysisexpert will be asked to consider a number of significant events and salient locations along with the call data records of a number of key mobile phones. The cell site expert may have conducted radio frequency surveys in support of the cell site analysis. From this information the expert will begin to report on the possible locations of mobile phones and indicate whether the evidence supports a set of circumstances or not. The issues that are considered on behalf of the Crown are usually those relied on as part of the prima facie case and may also include any comments made by a defendant during an interview or as part of a defence statement. The Defence instructions are likely to require some confirmation of the Crown case or to investigate an alternative set of circumstances or perhaps an alibi.
Regardless of who the work is prepared for, the cell site analysis evidence can only be effective if it is directed to answer specific questions. In the most simple of cases it may be relevant to state whether the call data records support an account that the user of a mobile phone was at a particular premises, a public house for instance. It is not the work of cell site analysis to identify who had usage of that mobile phone or what the user did or did not do at any location.
There is no designated style as to what the cell site analysis report should look like. Experts’ are required to conform to the contents of Part 33 of The Criminal Procedure Rules 2010 and should therefore produce their work appropriately. The Expert is required to summarise the findings on which are relied and to provide a summary of the conclusions reached. There are many other rules that are contained within the legislation but not subject to comment in this article. Accordingly we often seek the briefest of reports, a list of conclusions accompanied by maps and call schedules, not conforming to the Rules of the Expert and presumably compiled under the influence of cost or time constraints.
The second style of reporting is by systematically listing and answering a number of ‘scenarios’. These may be referred to as ‘contentions’ and effectively provide the format to show clarity between what is considered as important and the options of interpretation. Other styles of reporting indicate that the call data records are consistent or inconsistent with a certain scenario. Ultimately the cell site analysis report is prepared with a view of providing an interpretation of technical data which may assist a jury to consider a set of circumstances initiated by the Crown or the Defence.
So what of the ‘irritable inference’, arhetorical question that can derail the interpretation and findings of the cell siteanalysis Expert. Probably the simplest of statements, the Expert is told ‘but you have only considered one set of circumstances. You have not considered alternative scenarios’. The inference may be that the Expert has deliberately ignored other possibilities, or may have been incompetent, or worse still has deliberately provided biased testimony. It is unknown what the men and women of the jury absorb from this questioning. Is the testimony of the cell site analysis expert acceptable, or is the evidence to be considered dubious or unreliable?
The comment itself could appear to be harmless, but when considered further, if the instructions to the cell site expert have been fully provided then there is nothing that can be done to ‘guess’ or ‘speculate’ as to what could also be a relevant scenario. If a suspect does not mention an alibi in interview or within a defence statement, then why would a cell site expert be asked to consider whether the user of any particular phone could be at such an undisclosed location? Surely this is not incompetence or anything dishonest. We are all aware that the discipline of cell site analysis will not ‘pin-point’ a mobile phone and it is in the vast majority of cases that other locations will also be covered by cell identities.
Over recent years we have found occasions when the ‘irritable inference’ has become an ‘irritable irrelevance’. To explain further, this occurs usually whenwe have prepared the Crown report, the defence ‘experts’ provide an alternative scenario which may or may not have been introduced by the defendant. In one such case, we were questioned as to a particular call that ‘may’ have been conducted on a Motorway at a significant time when an offence took place in a neighbouring town. The particular call was significant to the Crown case and our cell site analysis report provided evidence that this would have been consistent with the phone being in the vicinity or at the scene of the crime at that time.
The defence ‘experts’ insisted that the call data was also consistent with the phone travelling along the Motorway, passing the area of interest. Instructions were given for ourselves to conduct radio frequency surveys along the same piece of Motorway introduced by the defence report. Those surveys confirmed that there was some cell identity coverage and that the defence scenario in itself had some credibility. However, there was a subsequent call less than one minute later; this was handled by a nearby mast orientated away from the motorway but near to the next junction. It was thought, by the Crown, that the usage of this cell identity was consistent with the offender using the mobile phone when leaving the scene after the crime had been committed.
The defence were guided to believe that this second call was acceptable to be consistent with passing the area and leaving the motorway and therefore supportive of an alibi. It has to be noted that this particular alibi was not provided at any time prior to the defence report being produced and it is not appropriate to comment on how this scenario become an option for consideration.
It was only after our engineer conducted the surveys on the Motorway that the ‘irritable irrelevance’ was exposed. The junction of the Motorway was permanently restricted, it was only possible to access the carriageway, and there was no exit for a further five miles. Accordingly the phone user could not have left the motorway and used the second cell identity for the subsequent call. The defence ‘alternative scenario’ was impossible. It should be clear that cell site analysis is capable of providing significant evidence in many cases, unknown alternatives cannot be commented upon and clear instructions to consider alternative scenarios should be fully reported on.
‘The Scales of Justice’ are themselves iconic. Anything other than truth and fairness will be found lacking. The duty of the Expert witness is well documented. Hopefully the good members of the jury will understand that the analysis of the unknown is too difficult even for the most experience cell site experts.
The words are now repeated; ‘but you have only considered one set of circumstances. You have not considered alternative scenarios’. It is not a question but may be more of an observation. If there is another scenario to consider then it would be relevant, no doubt further questioning would be forthcoming. However, on its own, it may be extremely damaging, misleading and pass unnoticed.
It is anticipated that the cell site expert will continue to be questioned as to why there has been reporting of certain issues whilst disregarding alternative but unmentioned accounts. Evidence must be relevant and the ‘scales’ must be in balance. What do you think?What do the jury think?
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