Legal journalist John Hyde, author of Indefensible: How lawyers failed to stop the Post Office Scandal, published on 15 September, says the legal profession must use this episode to reset its relationship with expert witnesses. John will be speaking at Bar Conference 2026 in '(Un)Reliable? The rule of expert witnesses' - a panel discussion which will consider how the role of experts has changed, the role of barristers in extracting the best evidence from experts, and whether and how expert witnesses should be regulated.
Among the many examples of lawyers failing to comply with their duties during the Post Office scandal, few are more egregious than the handling of expert witness evidence.
The trial of Seema Misra is the perfect case in point. This was a case of fundamental importance to the Post Office and its conveyor belt of Horizon-related prosecutions, largely because Misra had fought back, questioning the reliability of the IT system and based her defence on these questions of whether it could be trusted.
Gareth Jenkins was widely acknowledged to be the leading expert on Horizon and was called upon by the Post Office to talk up its reliability in numerous prosecutions, including that of Misra.
The prosecuting barrister, Warwick Tatford, was engaged in an email conversation in 2010 with Jenkins as they considered how Misra’s expert was trying to highlight problem with Horizon.
Jenkins told Tatford that he could not 100% rule out calibration issues with the system that could show up as discrepancies in the end-of-week balances.
Tatford replied: "Please rephrase. This will be taken as a damaging concession."
The barrister later tried to explain that he was trying to clarify matters with his expert witness but agreed he had "overstepped the mark". Jenkins did as requested and amended his statement to use stronger wording, asking of his instructing barrister: "Is that better?"
The impartiality of the Post Office’s go-to expert witness was clearly an issue during the many flawed prosecutions, not least because Jenkins was employed throughout by the Horizon designer Fujitsu. It seems extraordinary now that the courts did not question this relationship and demand extra safeguards to test the reliability of Jenkins’ evidence.
There were also clear failings in how the expert was instructed and even how he was regarded. Jenkins was officially treated – at least in the eyes of the court – as a witness of fact, but was referred to several times by Post Office lawyers as an expert, and concerningly even as "our expert".
Jenkins’ representative at the public inquiry, Clair Dobbin, said he had been entitled to trust the lawyers he was dealing with and to trust they were acting competently and lawfully.
"Mr Jenkins didn’t have the framework to know that what any of these lawyers were saying or doing was wrong or to challenge them," she said. "It’s important to emphasise, sir, that, in Mr Jenkins’ case, every single lawyer and investigator with whom he dealt was incompetent or acted in ways that was inconsistent with their duties."
One of the fascinations of the Post Office scandal is we have been able to peer behind the curtain to understand how the law was handled in practice. While the profession may publicly insist that lawyers understand their duties and carry them out, the disclosure of thousands of what were intended to be private emails has given us a peek into the reality of the short-cuts, loss of independence and unethical conduct that featured throughout the period of the scandal.
It would be naïve in the extreme to assume that the many failings of lawyers – including the inadequate instruction of expert witnesses – is not being replicated elsewhere. The Post Office was not unlucky enough to employ the only lawyers in the country who might have serious flaws.
We have seen several examples highlighted by the courts of expert witnesses being treated as advocates and – as Mr Justice Mostyn put it in Gallagher v Gallagher – walking ‘hand in hand’ with the client.
Supreme Court Justice Lord Hamblen said in 2022: "There is nothing more fatal to the acceptability of an expert’s evidence than the questions of independence and impartiality. It will taint all [and] it is therefore vital to avoid any hint of partiality."
These are laudable aims, but the Post Office suggested at a different truth: expert witnesses were treated as an extension of the prosecution team, their evidence able to be moulded to the point where it was most useful, and the duties they were supposed to act under not properly explained. It is an area where I suspect the public and profession’s perception varies: members of the public would expect experts to be impartial at all times, but many lawyers would privately admit that is often not the case. How many lawyers reading this would themselves have used the phrase 'our expert’?
The solution lies in enforcement and self-reflection. The courts should properly apply the clearly defined rules on how experts should be instructed and what is expected of them. The distinction between witnesses of fact and expert witnesses should be better understood. And the profession in general should use this as an opportunity for a reset. Expert witnesses should be there to ensure the right outcome is reached, not to act as a glorified cheerleader with letters after their name to lend the argument credibility. As a general rule, if an expert’s analysis undermines your case, the instinctive reaction should be to question your case, not to ask them to change what they are saying.
Book your ticket for Bar Conference 2026
Indefensible: How lawyers failed to stop the Post Office Scandal is published by Bristol University Press