On Tuesday, the Horizon Inquiry heard from Hugh Flemington, former head of legal at the Post Office. He was shown an email sent by Mr Jenkins on 25 February 2010.
Referring to a trial where he had been asked to give expert evidence, Mr Jenkins wrote: “This is another example of postmasters trying to get away with ‘Horizon has taken my money’.”
Mr Flemington told the Inquiry: “I was surprised when I saw this.” He said he couldn’t recall any request from the Post Office for expert evidence.
Mr Jenkins was later to give evidence in a number of cases, where he testified to the robustness of the Horizon system – evidence which was seen as crucial in winning those cases.
However, by 2013 concerns had been raised about his evidence. Barrister Simon Clarke wrote a memo circulated within the Post Office which warned that Mr Jenkins was aware of flaws in the Horizon system.
Knowledge of those bugs would have helped the defence in those cases, and Mr Clarke said the IT expert did not disclose them when he should have.
“[He] failed to disclose material known to him but which undermines his expert opinion… in plain breach of his duty as an expert witness,” Mr Clarke’s advice said.
It said his credibility was “fatally undermined”, and recommended that he did not testify in current or future trials.
Mr Jenkins is being investigated by the Metropolitan Police for alleged perjury.
A lawyer for Mr Jenkins told the in March it would be “inappropriate” for him to comment ahead of him giving evidence to the Inquiry in June.