Factual and Procedural Background
This opinion concerns an application by the prosecution under section 58 of the Criminal Justice Act 2003 for leave to appeal against a ruling by Her Honour Judge Lunt in the Crown Court at Preston. The ruling excluded evidence relating to the location of mobile phone masts through which certain calls were routed, which the prosecution sought to adduce in a conspiracy to supply controlled drugs case.
The Defendant was charged with two counts of conspiracy to supply controlled drugs, specifically diamorphine and cocaine, over a period from November 2016 to May 2017. Several co-accused pleaded guilty before trial, with the Defendant and two others proceeding to trial. The prosecution relied on surveillance evidence and mobile phone data, including cell site analysis, to link the Defendant to a particular mobile phone number allegedly used in the conspiracies.
The prosecution failed to serve cell site analysis evidence by the court-ordered deadline but served statements from two officers who collated and analyzed mobile phone data. The admissibility of this evidence was challenged by the defence. The judge directed skeleton arguments and responses, but the prosecution did not fully comply, leading to concerns about their preparation and adherence to court orders.
The judge excluded evidence relating to eleven specific occasions where the prosecution sought to link the Defendant to calls routed through particular mobile phone masts at postcode-level precision, citing the absence of expert evidence to assist the jury in understanding the technical aspects of cell site location and coverage. The prosecution was permitted to adduce evidence only at the broader town or city level.
The prosecution applied for leave to appeal the exclusion of this evidence, which was refused by the trial judge, leading to the current appeal before this court.
Legal Issues Presented
- Whether the trial judge erred in excluding evidence relating to the precise location of mobile phone masts without expert evidence explaining the technical aspects of cell site coverage and signal propagation.
- Whether the judge was wrong to require the prosecution to substitute specific postcode evidence with broader town or city-level information, potentially misleading the jury.
- The application and interpretation of section 58 of the Criminal Justice Act 2003 regarding prosecution appeals against evidential rulings and the conditions under which such appeals may be brought.
Arguments of the Parties
Prosecution's Arguments
- The judge was incorrect to distinguish between mobile phone data that could be understood by the jury without expert explanation (such as date and time) and data relating to the location of mobile phone masts, which the judge concluded required expert interpretation.
- The judge was wrong to require the prosecution to replace the specific postcode locations of mobile phone masts with broader town or city names, as this amounted to misleading the jury by removing factual evidence and substituting it with an interpretation.
- The observation evidence of police officers and the mobile phone service providers' data as to mast locations were agreed to be admissible by all parties, and exclusion under section 78 of the Police and Criminal Evidence Act 1984 was unjustified.
Defence's Arguments
- The prosecution conflated the location of a mobile phone mast with the proper inferences to be drawn about the phone's location, which required expert evidence to avoid misleading the jury.
- The judge appropriately balanced the risk that the jury, unassisted by expert evidence, would be unable to assess the reliability of evidence relating to precise mast locations against the prosecution's interest in adducing that evidence.
- The judge's ruling still permitted the prosecution to show the Defendant's movement between towns and the phone's routing through masts in those towns, preserving the core of the prosecution's case.
- Further evidence from the prosecution did not support their case that the Defendant was using the specific phone at the relevant times and locations.
Table of Precedents Cited
| Precedent |
Rule or Principle Cited For |
Application by the Court |
| R v Y [2008] 1 CrAppR 34 |
Requirement that the prosecution accept acquittal if the appeal is unsuccessful under section 58 of the Criminal Justice Act 2003. |
Confirmed the prosecution's acceptance of acquittal as a condition for bringing the appeal. |
| R v R [2008] EWCA Crim 370 |
Discretionary decisions by judges and the standard for appellate interference; acquittal agreement under section 58 appeals. |
Applied the principles that appellate courts will not interfere unless a decision is unreasonable; upheld the trial judge's discretion. |
| R v B [2008] EWCA Crim 1144 |
Exercise of judicial discretion in criminal trials and the high threshold for appellate interference. |
Supported the view that the trial judge's balancing of factors was reasonable and not perverse. |
Court's Reasoning and Analysis
The court analysed the nature of the evidence sought to be admitted by the prosecution, particularly the cell site analysis evidence linking the Defendant to calls routed through specific mobile phone masts. The court acknowledged that while basic mobile phone call data (date, time, duration) and general location (town or city) are generally uncontroversial and admissible, the precise location of a phone based on cell site data is a complex technical matter.
The court emphasised that expert evidence is commonly required to explain the limitations and variables involved in cell site coverage, such as mast directionality, range, overlapping coverage, and environmental factors. Without such expert evidence, the jury would be at risk of making speculative inferences about the Defendant's precise location based on mast data alone.
The court agreed with the trial judge that the prosecution conflated the location of the mast with the precise location of the phone user, which required expert assistance to properly understand. The prosecution's approach risked misleading the jury by inviting them to draw conclusions unsupported by expert evidence.
The court found the prosecution's argument that they were relying only on the coincidence of geographical proximity to be disingenuous, as the prosecution clearly wished the jury to infer that the Defendant was using the phone at the observed locations based on mast routing.
The court held that the trial judge's exclusion of postcode-level mast location evidence without expert explanation was a reasonable exercise of discretion aimed at ensuring fairness and preventing prejudice to the Defendant.
The court also rejected the prosecution's argument that substituting postcode data with town or city names misled the jury, finding that the jury would receive accurate information sufficient to understand the broader geographical context without being misled.
In sum, the court concluded that the trial judge's ruling was a correct and reasonable decision in the circumstances and that the prosecution's grounds of appeal were not properly arguable.
Holding and Implications
Leave to appeal is refused.
As a direct consequence of the prosecution's acquittal agreement under section 58 of the Criminal Justice Act 2003, the Defendant must be acquitted of the two counts of conspiracy to supply controlled drugs. The trial judge's exclusion of certain mobile phone mast location evidence is affirmed.
No new legal precedent is established beyond the application of existing principles regarding evidential rulings, expert evidence requirements, and the prosecution's obligations under section 58 appeals. The decision limits the prosecution's ability to rely on detailed cell site evidence without expert support to avoid unfair prejudice and ensure a fair trial.