Whether it’s CCTV, mobile phones or GPS software, digital evidence now plays a role in almost every criminal trial, so it follows that justice is ever more reliant on people being able to analyse technology and make arguments about what digital information means.
But experts speak of inequalities. On the one hand, the prosecution has an in-house service in the way of digital forensic units embedded in local police forces. But unless they’re self-funding, defendants are reliant on legal aid to fund independent digital forensic expertise.
Making matters worse, legal aid spending has been cut by 39.5% in real per-person terms between 2010 and 2024, according to the Bar Council. The result is that there are few experts able and willing to take on criminal defence work. “There’s no equality of arms,” said Tim Forte KC, a leading criminal defence barrister. “Everything we do is constrained unless the case is privately funded.”
The Westminster commission on forensic science, published this June, warned that caps on legal aid put justice at risk. Coupled with an “over-reliance upon police conclusions in digital investigations”, the report’s authors warned of bias against the defence.
Danny Kay’s story exemplifies what can go wrong. The prosecution relied on digital evidence to convict Kay of rape in 2013 – but it was only when relatives discovered deleted messages that a retrial was secured and his conviction was eventually quashed.
Separately, prosecution experts used signal data from Jodie Rana’s phone to argue she was at the site of an arson attack and secure her conviction in 2015. It wasn’t until a second expert demonstrated that Rana could have been much farther away that the conviction was annulled.
Defence advocates fear these stories are just the tip of the iceberg. “We are constantly battling for access,” said Forte. “It’s an ongoing fight where everything is hamstrung.”
Caps on legal aid
For many years, Forte’s preferred forensic investigator was Angus Marshall, a digital expert who doubles up as a lecturer at the University of York.
But Marshall no longer instructs defence barristers because the fees he can claim back on legal aid are so low.
On top of that, the cost of accreditation as a single practitioner is very high. “I stopped taking on case work two years ago because of the cost of compliance,” said Marshall. “The figures quoted to me were somewhere between £10,000 and £30,000, and I’d need to take on a quality manager. And my insurers won’t cover me without that accreditation.”
In total, Marshall was turning over around £25,000 per year on criminal defence casework, meaning the cost of accreditation would have bankrupted his business.
Forte told Computer Weekly that when the defence can’t find an independent expert to do defence work, a trial ends up delayed – or it goes ahead without any digital analysis to prop up the defendant’s side of the story.
Computer Weekly’s own analysis of court data found 4,264 instances of trials rescheduled between 2020 and 2024 because the defence was unprepared following late disclosure of evidence.
Forte said independent experts like Marshall, with decades of experience, are being forced out of the system.
Disclosure
Part of the problem is that the very devices analysed in court are chosen by the prosecution, according to Forte.
First, officers seize the digital devices they think might be relevant and then a digital forensic investigator (DFI) lists those considered relevant. The issue is that the defence might think differently about what’s relevant and what’s not.
Ian Ross, a forensic psychologist and expert in financial crime, said disclosure issues are rife in court. “Certain things are institutional,” he suggested, referencing his own years as a DFI at Greater Manchester Police.
“Police officers do not like to be seen to lose cases,” added Ross. “I’ve seen many, many cases collapse due to disclosure violations. People start tinkering around, playing games and withholding things.”
Analysis of Crown and Magistrates’ Court data suggests that 1,787 trials were rescheduled because the prosecution failed to disclose data between January 2020 and December 2024.
With digital evidence, Ross said that its technical nature is too often cited as an excuse for error. “We get excuses about how busy everyone is and how technical it all is,” he said.
He cited the infamous EncroChat trial – where European police officers implemented malware on an encrypted messaging service widely used by criminals at the time. Officers secured 1,240 convictions in 2020 – but they’ve refused to disclose their hacking software. Ross said that unless defence experts can forensically check their methods, any convictions are unreliable.
For Forte, working in a system unable to facilitate equal access to digital evidence is both “stressful” and “frustrating”. Much of his time is spent “putting out fires”.
“Over the last 10 years, my go-to phrase has been that I’m dealing with the crocodile closest to the boat,” he said. “Out of necessity, everything else is on the backburner.”
A spokesperson for the Ministry of Justice (MoJ) said: “We understand the importance of high-quality, timely forensic evidence for an effective criminal justice system that prevents crime, prosecutes suspects and gives victims the justice they deserve.
“That’s why we are appointing a national forensic science lead who will transform our approach to raise standards and improve efficiency, and ultimately build greater public confidence in our criminal justice system.”
A Crown Prosecution Service spokesperson said the body had nothing to add to the MoJ statement. The Forensic Science Regulator and the National Police Chiefs’ Council did not respond to a request for comment.
