Admissible vs Defensible: What Accreditation Means for Digital Evidence

Digital evidence is everywhere: in mobile phones, laptops, cloud accounts, messaging apps, and even network data. But in court, it’s not enough for evidence to simply exist. It must be handled, examined, and reported in a way that withstands scrutiny.

That’s where the difference between admissible and defensible matters.

A file extraction might be admitted into proceedings, but if the opposing side challenges how it was obtained, preserved, or interpreted, the weight of that evidence can quickly unravel. For solicitors, investigators, and legal teams, the real question becomes:

Can this defensible digital evidence withstand challenge?

One of the clearest indicators of that defensibility is whether the work was conducted under ISO/IEC 17025, assessed by UKAS (the United Kingdom Accreditation Service).

What ISO/IEC 17025 is (and why it matters)

ISO/IEC 17025 is the international standard that sets out the general requirements for the competence of testing and calibration laboratories – including digital forensic laboratories.

Put simply, it’s a recognised benchmark for proving that a laboratory is working to documented, repeatable, quality-controlled processes, and that its outputs are reliable.

In the UK forensic space, ISO/IEC 17025 is closely linked to confidence in evidence used within the Criminal Justice System, and accreditation is overseen by UKAS.

While clients often view accreditation as a “badge,” it’s more useful to think of it as a framework that reduces risk, because it requires evidence handling to be:

• Competent (appropriately trained practitioners)
• Controlled (validated methods and tools)
• Transparent (auditable, documented processes)
• Repeatable (consistent outputs under the same conditions)

In practice, ISO 17025 accreditation supports ongoing internal review and independent external assessment… not just a one-off tick-box exercise.

CYFOR is accredited to ISO/IEC 17025, reinforcing our commitment to technical excellence and quality management across digital forensics.

What gets challenged in digital forensic evidence

When digital evidence is disputed, challenges typically fall into a few predictable categories. Knowing these helps solicitors instruct the right provider and helps providers deliver reports that remain robust under pressure.

1) Continuity and handling

Even strong evidence can be weakened if it’s unclear who handled a device, how it was transported, and what happened to it between seizure and examination.

Common challenge themes include:

• Gaps in handling records
• Unsealed packaging
• Poor storage conditions
• Lack of documented device state at receipt

2) Method and tool reliability

Opposing experts may question:

• Whether the technique used was validated
• Whether the tool is fit for purpose
• Whether the examiner applied the method correctly

This becomes especially relevant for mobile device acquisition and advanced extraction work, where different tools can produce different results depending on device type, security settings, or operating system changes.

3) Interpretation and reporting

Sometimes the extraction is sound, but the conclusions are not.

Challenges often focus on:

• Overstated findings
• Missing limitations
• Misinterpretation of timestamps, app artefacts, or user activity
• Failure to explain uncertainty clearly

4) Disclosure and reproducibility

Courts expect that digital forensic work can be understood and, where appropriate, reproduced or reviewed. Where artefacts are poorly explained, or the process is unclear, credibility can suffer.

How labs reduce risk (and protect the case)

ISO/IEC 17025 won’t stop evidence being challenged. But it does make it far less likely that a challenge will succeed.

Documented, audited processes

Every step is recorded and repeatable – so you can show exactly what was done, when, and why.

Validated methods and tool control

Methods and tools must be proven fit for purpose, with checks in place to reduce errors, inconsistencies, and tool-driven disputes.

Competence and training controls

Examiners work within defined scopes of competence, backed by training, assessment, and supervision.

Stronger defensibility under the FSR framework

In England and Wales, the Forensic Science Regulator’s statutory Code of Practice links to accreditation expectations, including assessment by UKAS where required.

Cell site analysis is moving the same way

Cell site analysis is increasingly being held to the same standards as other forensic disciplines. CYFOR is working towards extending accreditation in this area – keeping our work defensible and putting us ahead of many providers still operating without it.

Questions solicitors can ask when instructing a digital forensics provider

If you’re instructing digital forensic work for criminal defence, prosecution, family/childcare proceedings, or a corporate investigation, here are practical questions that quickly reveal whether evidence is likely to stand up in court:

Accreditation and scope

• Are you UKAS accredited to ISO/IEC 17025?
• What exactly is your scope of accreditation (and does it cover the work I need)?
• Are there any parts of the examination that fall outside your accredited scope?

Evidence handling and continuity

• How do you document chain of custody from receipt to return?
• How are exhibits stored, sealed, and secured?
• What courier or collection procedures are used?

Method and reporting defensibility

• What forensic tools will be used and why?
• How do you validate your processes and quality-check outcomes?
• Will your report clearly state limitations and assumptions?

Court readiness

• Can you provide an expert witness if required?
• How do you present complex evidence in a way the court can understand?
• What’s your approach if evidence is challenged by an opposing expert?

Conclusion: defensibility is the real benchmark

In legal proceedings, the goal isn’t simply to produce “digital evidence.” It’s to produce evidence that can survive challenge and retain its value.

Accreditation helps reduce risk by supporting controlled processes, competence, and transparency – all of which matter when evidence is tested under courtroom scrutiny in a digital forensic laboratory.

If you’re instructing a digital forensic expert and want confidence that the evidence will remain defensible digital evidence, speak to a provider that can demonstrate quality as well as capability.

Need support with a digital forensic instruction?

CYFOR’s UKAS-accredited team can advise on the most appropriate approach for your case and help ensure digital evidence is handled correctly from day one.