IT and digital forensics expert, Jason Coyne, was an Expert Witness in the sub-postmasters’ case against the Post Office’s Horizon computer software. He first spotted errors in the Horizon system in 2003, but had his findings dismissed by the Post Office. He tells us more about his involvement in the case, the wider impact on his work as an expert, and finding himself in the limelight.
How did you first get involved in the Post Office case?
In 2003, I was instructed as a Single Joint Expert by the Post Office to examine Horizon computer system data from the Cleveleys Post Office branch in Lancashire. The sub-postmistress there, Julie Wolstenholme, was being pursued for £25,000 for losses at her branch. I was instructed to assess whether Julie was responsible for those losses. They probably chose me because I was relatively local to the area and one of only a few Expert Witnesses specialising in technology back then.
I requested certain evidence – things like call logs, comparisons between branches, and audit logs – to help form my opinion. But I was told by the Post Office that this information wasn’t available.
Instead, I was asked to opine based on the evidence I’d been provided. I had been given some call logs and it was obvious from those that Julie had found a number of errors which could be impacting her branch accounts. I wrote an interim report stating that in my opinion, 61 out of 90 bugs, errors, or defects were as a result of the Horizon system.
The expectation was that I would be given more evidence to assess before I converted my interim report to a full report. But before that could happen, the Post Office and Julie Wolstenholme came to an agreed settlement. So the case didn’t go to court, a confidentiality agreement was placed on Julie, and my report didn’t see the light of day for another 20 years.
Was the Post Office initially supportive of your investigation? When did that change?
It was clear that the Post Office didn’t like what I’d found, because they asked if I would be willing to revise my opinion if I had the chance to review additional evidence. This proposition isn’t unusual in Single Joint Expert matters. Someone is often disappointed in how the expert report has turned out and will try to present new evidence. Remember that at the time, no one knew the Horizon issue was a big scandal.
I said I was happy to take on new evidence and listed the exact evidence that I needed. But the Post Office offered me a meeting with Fujitsu and a look around its data centres. I said we were talking about a very specific Cleveleys Post Office branch — I wanted to know what was happening there. Fujitsu’s data centre and its operations wasn’t relevant to this particular case. The Post Office couldn’t provide the evidence I asked for, so I said my report stood as it was.
When the case settled out of court, there was actually a sense of happiness. I believed that the process stopped because the parties saw that there wasn’t a case to answer. So back then, I wasn’t disappointed — I was pleased.
In 2016, you were instructed as an Expert Witness by the claimants against the Post Office in the Bates vs Post Office litigation. How did it feel to be involved again years later?
At first, I didn’t put two and two together that it was the same case! The opportunity to get involved again came about when I met James Hartley of Freeth’s [the law firm who acted on behalf of the sub-postmasters] at the Yorkshire Legal Awards. James said he was trying to assemble a group of sub-postmasters and had a highly technical matter that they needed some experts to look at. I said I was happy to take that on and started to get involved.
Given that you’d already formed an opinion that the Horizon software was faulty, was it hard to stay impartial in the Bates vs Post Office litigation?
The need to be impartial as an Expert Witness is always at the forefront of my mind. My opinions have to be completely independent and I make sure I’m confident that I would have said exactly the same things regardless of who had instructed me. As long as the court has all the information and the range of opinions to make a decision, then your job as an expert is done.
During the Bates vs Post Office litigation, you were cross-examined for four days. Had you been involved in such an extensive cross-examination before?
I’d never been cross-examined with that level of intensity before, but overall it went really well. Judge Fraser noted in his judgement that I emerged largely unscathed, which I think is an endorsement for my performance in the witness box! I knew that because of the amount of time I spent preparing and the level of research I did, the barristers wouldn’t have the level of detail that I had.
I have an ability to be able to hone in on technical detail and that cross-examination was all about technical detail. I knew I was as strong as I could possibly be, largely due to the number of hours I put into it.
There was only one occasion where I got flustered, because I was given what became a maths test! I don’t know why I went down that route of starting to find the answer. It served as a reminder not to step away from my area of expertise.
What are the keys to being successful in a cross-examination of such length and complexity?
Don’t be defensive. If anyone is challenging you, you have to listen to them and consider what they’re saying. If, having examined the evidence again, your opinion is unchanged then that ultimately puts you in a stronger position.
Don’t allow yourself to be rushed. Counsel will sometimes jump in when you’re halfway through giving your opinion. They often just want a yes or no answer without any qualification. That happened in the Post Office litigation and the barrister got told off on a few occasions with the judge putting him in his place.
Keep your cool. Make sure you understand the questions that are being put to you. If you don’t understand the question or its too complex, ask counsel to put it in more simple or direct terms. Questions are designed to trip you up or expose weaknesses. Judges will always be sympathetic to that.
Bring your own copies of documents. I like to have paper bundles available of at least my own report with me in the witness box. If the barrister is the only one going through the documents and you don’t have your own to reference, you lose control.
At the 2023 Post Office Horizon IT inquiry, it was heard that the Post Office tried to dismiss your 2003 report as a “very one-sided view” and “very unhelpful”. How did you feel when you saw that they had tried to discredit you?
I felt frustrated. Because if the people who were trying to discredit me had just accepted the findings in my report and provided the evidence that I’d asked for back in 2003, the outcome would have been very different.
When I wrote the report, I didn’t know they’d tried to discredit it. The first time that I got to see the internal communication that went on at the Post Office was at the inquiry, 20 years on!
My original report wasn’t even brought up at the Bates vs Post Office litigation in 2019. It should have come up in disclosure, but didn’t. The Post Office didn’t disclose it because they either couldn’t find it, or it was part of a cover up.
The Horizon scandal could have been stopped it the Post Office had acknowledged that an independent expert had found bugs in the system. Rather than take my report and change things, they chose to bury it. Somewhat tellingly, they never appointed independent Expert Witnesses again, choosing instead to use Fujitsu employees.
What advice would you give to an independent expert whose findings were being rejected by their client?
When you’re appointed as a Single Joint Expert, you accept that 50% of the parties involved are probably going to be disappointed with your expert evidence. If you’re going to be fully independent, you do have to accept that half the time you’ll have been instructed by the party who lost the dispute. You don’t always have to be seen as being right.
The ITV drama Mr Bates vs the Post Office sparked public interest in the case. What was it like to suddenly be in the limelight for Expert Witness work?
Not a lot of people outside the legal profession understand Expert Witness work, so it’s been great to put our work in the limelight. It’s been good to have a platform to help the wider community understand how we operate, show our role in litigation, and get across that people like us exist outside of shows like CSI!
Has the Post Office case changed your approach as an expert?
I wouldn’t say it’s changed my approach. But it has shown me that in complex cases, teamwork is key. In the Post Office case, many millions of documents needed to be examined. Building an Expert Witness investigations team was what we did as part of that investigation and that’s something I’ve adopted going forward. All my systems are far better today as a result of the Post Office case.
Unusually, Judge Fraser’s first task for us two experts in the Bates vs Post Office litigation was to come up with the issues we wanted to consider.
We mapped out the issues, took them back to the managing judge, and they were the issues taken forward. I believe that Judge Fraser wanted to ensure that it was the experts who decided which issues needed to be considered to address the parties’ dispute, rather than the lawyers.
I think taking this approach is logical, rather having opposing legal teams instructing separate experts to focus on issues largely supportive of respective cases. This usually results in separate reports that read as though they have looked at different evidence – and often requires further rework later.
The technology experts in a technology case defined what we should look at and that worked really well as a framework.
Taking the driving seat as an Expert Witness is an approach I try to apply in my other cases now. I try to get the lawyers on board, so that they advocate for this process at one of the pre-trial hearings. Then there’s the chance that the judge will build it into the process.