Cell Site Analysis – The Importance of Defence Expert Evidence

Following a recent blog published outlining the relevance of cell site analysis in criminal investigations, this blog aims to outline the importance of obtaining expert input early in respect of cell site evidence that may form part of a criminal investigation.

Cell site analysis is a forensic method used by police intelligence analysts to identify where a mobile phone could have been at a particular time. As part of the Crown’s evidence, call data records may be supplied. These are produced by the network provider and are originally intended for billing purposes. Phone activity is logged on the device so it can be charged for by the provider. From this, with reference to phone masts, it is possible to work out where a phone, and therefore the phone owner, may have been.

Many issues arise with evidence that may be served initially by the prosecution. For example, a map of masts may be provided to the prosecution.

It may be a fact that a particular phone was near a particular mast at a certain time, however, it may not be true that the particular phone was used at that certain time.

Observations made by the Crown when preparing their case do not automatically translate to a confirmed conclusion, which is why there is significant danger in leaving cell site analysis data uncontested.

Challenging call data records 

The Court of Appeal has highlighted the dangers of taking call data records at face value. It is always important to seek an expert to consider what information is supplied by the prosecution as it may, simply put, not be actual evidence.

In R v Calland [2017] EWCA Crim 2308, the defendant was charged with two counts of conspiracy to supply a controlled drug. The prosecution attempted to rely on evidence regarding the location of the defendant’s mobile phone masts used for calls relating to the alleged offence. The defence applied to exclude the evidence of billing records and observations based on mast locations, arguing that this was not definite to show that he had used the phone at the relevant time for a criminal act. The court agreed and excluded the records.

The Court of Appeal held that this was the correct course of action. The prosecution had failed to obtain their own expert evidence to offer expert opinion to the jury based on the information they attempted to rely on. The information served was only speculative, and in the absence of any formal expert opinion, a jury could not be guided to draw a conclusion based on properly affirmed evidence.

Opinion evidence from an expert is expert evidence. Cell data records, mast location maps and other similar information in isolation cannot be treated as standalone expert evidence or as a report.

Forensic Science Regulations and the Criminal Procedure Rules 

In cases where the prosecution may supply an expert report in conjunction with call data records, maps etc, it is important to assess that the expert report complies with the Forensic Science Regulations and the Criminal Procedure Rules. A failure to comply can render an expert report inadmissible in proceedings.

Whilst aspects of the FSR Codes are not fully in force until October 2025, the Criminal Procedure Rules are in full effect and govern all expert reports. Experts must include:

• The expert’s qualifications, accreditation and relevant experience;
• Any literature or other information they have relied upon to prepare their report;
• A statement setting out the substance of all facts given to them;
• Which facts in the report are within the expert’s own knowledge;
• Where the expert has based an opinion or inference based on fact of opinion made by another (for example, as to the outcome of an examination);
• Where there is a range of opinion, a summary and reasons for their own opinion;
• A summary of the conclusions reached; 
• A full statement declaring their duty to the court and a declaration of truth as a witness statement.
• A defence expert will consider whether there is full compliance with the Code and Criminal Procedure Rules as part of their instruction.

What if my case involves cell site analysis?

It is vital that defence expert opinion is sought as soon as possible in cases where cell site analysis is presented. The prosecution may often obtain maps of mast locations and tables demonstrating call logs but these in themselves are not expert evidence.

Olliers Solicitors – specialist criminal defence lawyers

At Olliers, our serious crime department has extensive experience in representing clients who face allegations which involve cell site analysis including allegations of drugs supply and murder and manslaughter offences. We have positive working relationships with a number of defence-focused experts and will be on hand to guide clients through the often complex issues associated with cell site analysis and telephone attribution.

If you require advice in relation to serious criminal cases, please contact our new enquiry team either by email at info@olliers.com, or by telephone at 020 3883 6790 (London) or 0161 834 1515 (Manchester) or by completing the form below and our new enquiry team will contact you.