Cell site evidence: What happens when opinion is offered without a proper evaluative framework

When instructed by Defence to review telecommunications evidence in a shooting, concerns were identified regarding the interpretation of cell site evidence and the distinction between expert opinion and technical observations.

The case highlighted an issue that had long existed within the discipline – and remains relevant today: practitioners routinely report technical observations concerning network activity, but the reliability of resulting opinions, and the consideration of alternative explanations, is not explicit.

CCL undertook an examination to test the validity of methods and the approach to reasoning underpinning the prosecution material. Rather than relying upon a purely technical analysis, conclusions were examined in the context of competing explanations and with a view to the validity of the method used.

The review explored the role of expert opinion in cell site analysis, the boundaries of interpretation, the effect of ‘false negative’ survey results and the importance of transparent reasoning when presenting evidence to the court. The implied position from the initial product was that the scene and alibi locations could be distinguished from one another using the survey data; the review showed they could not. This view was expressed in oral evidence, and the accused was subsequently found not guilty.

The findings were subsequently developed into the peer-reviewed paper Opinion Evidence in Cell Site Analysis, published in Science & Justice. The work contributed to wider professional discussion surrounding evaluative interpretation, transparency and scientific robustness; and the methodology adopted during the examination established principles that would later be formalised within FSR-GUI-0004 (Forensic Science Regulator’s guidance document - ‘Forensic science activities: interpretation and communication’).

Key outcomes

• Led to oral evidence that was deemed to have contributed significantly to the defendant being acquitted
• Identified limitations in traditional approaches to cell site interpretation
• Demonstrated the importance of transparent reasoning and evaluative interpretation
• Formed the basis of a peer-reviewed publication in a leading forensic science journal which received national recognition from the Chartered Society of Forensic Sciences and was presented to the Royal Statistical Society at their annual conference
• Contributed to professional debate regarding opinion evidence in telecommunications analysis