Exclusive: Horizon Scandal Expert Reveals Critical Evidence in Murder Case
A former Fujitsu developer who warned about critical faults in the Post Office's Horizon computer system has revealed new information that could potentially overturn a murder conviction. David McDonnell, who held a key role at Fujitsu before the Post Office rolled out Horizon in 2000, has raised serious concerns about Robin Garbutt's 2011 prosecution for the murder of his wife Diana.
The Horizon System's Flawed Foundation
David McDonnell served as deputy development manager at Fujitsu's UK office in Feltham, Greater London, from 1998 to 2000. During this crucial period before Horizon's implementation across Post Office branches, he repeatedly warned about significant faults in the system but was ignored by management.
"The system had been compromised and they should have been honest about that at his trial," McDonnell told the Mirror. "Robin Garbutt was asked about taking money from the till based on unreliable financial data. It means the two prosecution financial experts were also wrong."
McDonnell emphasized that Garbutt was never prosecuted for theft, which he considers "always the big giveaway in these cases." He believes prosecutors knew they could not rely on financial evidence from the Horizon system but proceeded anyway.
A Conviction Built on Faulty Evidence
Robin Garbutt, now 60, has served 15 years of a life sentence for the murder of his wife Diana, who was bludgeoned to death with a metal bar at their post office in Melsonby, North Yorkshire, on March 23, 2010. Garbutt has consistently maintained that his wife was killed by a robber during a break-in.
The prosecution's case heavily relied on Garbutt's alleged financial troubles, with evidence drawn from the now-discredited Horizon system. Mark Baker, a former sub-postmasters union official with 38 years of branch experience, explained how this evidence impacted the jury.
"It was quite impactful for the jury," Baker said. "If they thought you had too much cash, you got automatic requests from Horizon to give what you had spent back. But a lot of postmasters ignored it because it was wrong. It was common behaviour to do that."
Technical Failures and Legal Consequences
McDonnell provided detailed testimony to the official inquiry into the Horizon scandal, revealing that he co-wrote a report highlighting serious errors in the system's programming and code. His assessment was damning.
"It was so bad. It was beyond anything I've ever seen," McDonnell told the inquiry. "Even in the 25/30 years since that project, I've never seen anything like that. Some of the stuff that we found buried in the code was unbelievable. There was unreachable code... It was a mess."
The Horizon system's failures led to the wrongful prosecution of more than 900 postmasters based on faulty financial data. McDonnell believes these same systemic issues contaminated Garbutt's murder trial.
The Fight for a Retrial
Garbutt has submitted a fourth application to the Criminal Cases Review Commission (CCRC) in a bid to take his case to the Court of Appeal. He seeks a retrial to definitively clear his name. After one earlier application was rejected, Garbutt expressed his frustration: "I feel like I have let Di down again. The killers are still out there."
Dr Mike Naughton, an academic and legal campaigner, has criticized the CCRC's handling of the case, noting that the commission has rejected new evidence in three previous applications.
"It is 'computer says no, computer says no, computer says no'," Naughton said. "Yet the evidence that led to the conviction has been discredited in my opinion."
Forensic Gaps and Family Support
Significant questions remain about the forensic evidence in the case. Dr Naughton stressed that there was "no forensic evidence whatsoever" linking Garbutt to the murder scene. The murder weapon, a metal bar, was found to have the DNA of a North Yorkshire police officer on it after he discovered it on a wall opposite the post office two days after the murder.
Adding to the mystery, a press photo of officers in Melsonby on the day of the murder shows that the metal bar used to kill Diana does not appear to be in the spot where it was later found.
Garbutt's family continues to support his fight for justice. His sister Sallie Wood and brother-in-law Mark Stilborn, who tragically died last year, emphasized that Garbutt wants more than just freedom.
"He wants a retrial to prove that he has not done this," Sallie said. "He wants a retrial to prove that beyond any doubt."
The CCRC confirmed it has received Garbutt's latest application and that a review is underway, while rejecting "any suggestion that they are not committed to the job." North Yorkshire Police stated they have nothing to add to the facts presented in court, which "resulted in Robin Garbutt being sentenced to life."
As the Horizon scandal continues to unravel, David McDonnell's revelations add another layer to one of Britain's most controversial legal cases, suggesting that a murder conviction may have been built on the same faulty evidence that destroyed hundreds of postmasters' lives.
