Your Expert Q&A: Cell Site Analysis

Cell Site Analysis continues to evolve. With the Forensic Science Regulator’s Code of Practice and DIG200 in force as of October 2025, compliance is no longer optional.

Methods, standards and expectations are all shifting as practitioners refine how cell site evidence is analysed, presented and challenged.

For anyone needing a clear, up-to-date view of where things stand, this Q&A offers a rapid way to get expert insight from one of the world’s leading authorities on Cell Site, Dr Matt Tart.

An essential read for anyone working in investigation, prosecution, defence or the wider criminal justice system.

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Matt, before we get into the detail – why should people trust your take on Cell Site Analysis?

I’ve worked in Cell Site Analysis for decades now, and it’s something I’m genuinely passionate about. A claim to fame is that I was the first person in the world to get a doctorate in the subject so yes, this is something that I have lived and breathed for a while now. I’ve published a lot of the foundational academic work that’s helped shape how the field operates today. I’m also actively involved in quality and standards via membership of groups run by BSI and the Forensic Science Regulator.

I’m a member of the Cell Site team at CCL; we’ve been independently assessed as compliant with the Forensic Science Regulator’s Code, and we hold UKAS accreditation for DIG200 – the recognised standard for Cell Site Analysis under the Code. We’ve had accreditations across multiple areas of forensic science for more than a decade, so for us this isn’t a badge to chase – it’s simply the way we work.

Ultimately, this matters because what we do has real impact on people’s lives and on justice. That’s what drives the team and me: doing it properly and setting a standard everyone can have confidence in.

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What exactly is DIG200 and why does it matter in Cell Site Analysis?

DIG200 is the required standard for Cell Site Analysis, set by the Forensic Science Regulator, and compliance with it is now a requirement. If the work doesn’t meet that standard, it’s by definition sub-standard – it presents a risk to the Criminal Justice System.

A mistake we still see is people presenting maps and tables as if they can be taken at face value. They usually can’t. Without technical interpretation and then stated opinion on what it all means, that evidence falls short of the Code of Practice. And when opinions are given, they need to be supported by validated methods and demonstrable competence – not just “experience” or confidence.

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How can organisations be confident their Cell Site provider is compliant?

The best starting point is to ask for proof. Can they demonstrate UKAS accreditation for DIG200? Are their methods independently audited and validated? It’s easy enough to check providers via the UKAS website, where we’re listed as CCL Forensics.

At CCL, we’ve built our processes to be transparent, robust and verifiable. We combine detailed technical knowledge of call data with sound survey methods and a clear understanding of what it means to be an expert witness. We invest heavily in research and technology to go beyond compliance and give clients confidence that the evidence is both reliable and fair.

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A lot of people think Cell Site is just about producing maps – is that right?

That’s probably the biggest misconception. Producing maps is just one part of a process, but on its own, it’s just not enough. What really matters is in the interpretation: setting appropriate propositions and then forming opinions that are logical, balanced, robust and transparent. In Forensic Science, those words aren’t throw-away terms, they mean something specific. Without that, you just have a bundle of data that looks impressive but might actually mislead.

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What makes CCL’s opinion evidence different?

First and foremost, it’s based on research and data, not assumption. We’ve published in peer-reviewed scientific journals, and one of our papers on opinion evidence was even commended as one of the most meritorious in forensic science that year.

We use the Case Assessment and Interpretation (CAI) model, which is recognised by leading scientific bodies as best practice. Our conclusions are informed by one of the UK’s largest Cell Site measurement databases - around a billion data points - so our evidence is grounded in real network behaviour.

We’ve also got a fantastic team with more than 150 years of combined expertise, and we build quality checks into every case. That means opinions aren’t based on one person’s view: they’re tested, reviewed, and collectively owned.

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Where is forensic science, and specifically Cell Site Analysis, heading?

It’s an interesting time. There’s a lot of scrutiny, and reports from Parliament and the House of Lords have been pretty frank about where the system needs to improve. But that’s also a real opportunity to raise standards and restore confidence.

One of the key recommendations is that forensic science should be carried out by independent experts, using validated methods in externally assured environments. That’s exactly how we work at CCL - objective, quality-driven, and independent of any investigative bias.

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You’ve previously said “pick your hard” when it comes to validation, competence and bias – what do you mean by that?

Doing it properly takes effort. Validating methods is hard. Maintaining competence is hard. Controlling bias is hard. But the alternative - not doing those things - creates far bigger problems that are much, much harder to address. That’s when mistakes happen, potentially even miscarriages of justice, and it’s incumbent upon all of us within the Criminal Justice System to avoid those scenarios.

So yes, it’s demanding work, but it’s the right kind of demanding. And as of October 2025, compliance with the Code became mandatory as the system aims to protect fairness for everyone. There can be no more talk of falling into line next month or next year; the time is now.