Related Sector: Expert Witness, Witness Familiarisation

The ongoing Post Office Horizon IT Inquiry has recently revealed how a senior Post Office lawyer told an engineer working on their defective IT system to provide a court with evidence that would help with ‘’preserving’’ it. This led to the jailing of a wrongly convicted and pregnant subpostmaster, Mrs Misra, in 2010.

Warwick Tatford, the prosecuting barrister in the 2010 case told the Inquiry that the advice sent by the Post Office lawyer was ‘’disastrous’’. He added, ‘’As far as I’m concerned, I was prosecution counsel in the case… and I have obviously failed to ensure that there’s an atmosphere where an expert can be properly instructed.’’

Whilst the Inquiry deals with many issues relating to the failings of this IT system, this article will focus purely on the instruction of the engineer as an expert witness in the case – specifically what is deemed necessary by the courts as a proper instruction of an independent expert witness.

The ‘instruction’

While giving evidence in the Inquiry, Mr Tatford was shown the email from the Mr Singh, the Post Office lawyer to Mr Jenkins, the ‘expert’, which read:

“As you are our Horizon expert you need to telephone Charles McLachlan [the defence expert] …to arrange a meeting where you can discuss all his reports and his concerns about the Horizon so you can deal with it and rebut it.”

The email continued: “… and then write a detailed report which would go to some way of progressing and concluding this matter and importantly preserving the Horizon system…Maybe the simplest and practical way of dealing with this whole question is to find a shortest span of logs, analyse it, disprove or rebut what the defence expert is saying in his reports.”

“Just a reminder you are an expert for Fujitsu, you will be giving evidence in court, the judge and jury will be listening to you very carefully and a lot will hang on the evidence.”

The Inquiry

The Inquiry considered the details of Mr Jenkins’ instruction as an expert witness.

Initially, they confirmed the duty of a prosecutor in relation to an expert witness, that a prosecutor intending to rely on expert witness in criminal proceedings must:

  1. Satisfy themselves as to the expert’s relevant qualifications and expertise.
  2. Satisfy themselves that the expert had been appropriately instructed, including by the provision of a written and detailed letter of instruction or an email of instruction, all being provided with written terms of reference.
  3. Satisfy themselves that the expert was provided within their instructions, what it is that his or her opinion is sought on and set out issues or questions that he or she is expect  to answer.
  4. Provide guidance as to what the expert is being asked to do and what material they are being asked to consider.
  5. Set out the material upon which reliance has been placed in the prosecution and which may be relevant to the questions which the expert is expected to answer.
  6. Must inform the expert witness as to his or her relevant duties and ensure that the expert understands and has complied with those duties.

Then, the Inquiry led Mr Tatford through the details of Mr Jenkin’s instruction, highlighting the following failures:

  1. There was no documentary record confirming that Mr Jenkins understood the relevant expert duties and no documentary record which confirms that any prosecutor was satisfied that Mr Jenkins understood the relevant expert duties.
  2. That Mr Jenkin’s expert report did not comply with the relevant provisions in the Criminal Procedural Rules.
  3. That there was no appreciation of risk, bearing in mind that the expert’s day job was not expert witness and in fact an engineer working on the Post Office IT system – and therefore that they might have ‘’skin in the game’’. As confirmed by Mr Tatford, ‘’he went from one day, as I understood it, to the person who was helping with disclosure enquiries, to becoming our expert.’’


Expert witnesses are independent parties who owe a duty to the court and not the party who instructed them.

This Inquiry highlights how important it is for an expert witness to be independent from any of the parties in a case, and the dangerous consequences of an improper instruction. As emphasised above, the onus isn’t just on experts to ensure that they are aware of their legal duties, but also on the legal teams as well. Giving evidence in the Inquiry, Mr Tatford, the prosecuting barrister in the 2010 case, held back tears, saying he was ‘’ashamed that I was part of this’’, before apologising to Mrs Misra who sat in the public gallery.

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