The £1 billion Fujitsu Horizon system has been subject to huge controversy, as over 150 subpostmasters prosecuted for theft or false accounting claim problems with Horizon caused the errors.
The Post Office is still refusing to hand over prosecution files to forensic accountants Second Sight, who were appointed to independently investigate the matter in June 2012, forensic computing expert Henderson said during a select committee hearing.
The Post Office’s head of partnerships Angela van den Bogerd said: “We have been working with Second Sight over the last few weeks on what we agreed at the outset. We have been providing the information.”
But when asked “is that right?” by committee chair Adrian Bailey MP, Henderson replied: “No, it is not”.
Henderson claimed the Post Office had brought investigations against subpostmasters with “inadequate investigation and inadequate evidence”.
“In particular we are aware, and this is why we need the prosecution files, a common tactic by lawyers is to bring charges of false accounting and theft.
“False accounting is easy to prove, so for plea bargaining you offer to drop the charge for theft, as firstly the defendant will avoid a custodial sentence and the evidence to prove the case is simpler.”
Henderson said an interim report into Horizon had found the system had about 12,000 communication failures every year, software defects at 76 branches and old and unreliable hardware.
He added: “There are fallback procedures but some rural branches have broadband problems and poor mobile phone signals.”
He said problems with Horizon were “relatively rare” but he explained issues could be caused by “an unusual combination of circumstances such as power and communication failures, or errors at the counter”.
Henderson said many subpostmasters felt they “had no option” but to enter false figures into Horizon and their behaviour had been “perfectly understandable”.
However van den Bogerd said: “The helpdesk was available until 10pm and they could leave a message…they had a choice to tell us, so it was a conscious decision they made [to enter false figures].”
Paul Blomfield MP accused the Post Office of having a “culture of denial about problems”.
“As long as Post Office is controlling all of the information, we’ll never find out all of the truth,” said Alan Bates, chairman of Justice for Subpostmasters Alliance, which represents the affected subpostmasters.
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