On the last day of the committee stage for the Data Bill in the House of Lords before the Christmas break, we made a strong push for the government to rethink how computer evidence is treated in legal cases.
Right now, UK law assumes that when computers produce evidence, they’re working correctly. Sure, you can challenge that assumption, but that often requires access to the computer system—a tough ask for those who don’t have it. It’s surprising that this hasn’t been resolved yet, especially after the troubles from the Post Office Horizon scandal last year. My colleagues and I are using this Data Bill as a chance to address this serious issue head-on. During the second reading, I asked, “What’s the government’s stance on reversing the burden of proof for computer evidence? It should definitely be verified.”
Now, let’s get real about computer evidence. As barrister Paul Marshall, who represented some of the subpostmasters caught up in the scandal, pointed out, we can’t take computer evidence at face value; it’s often hearsay, with all the limitations that come with it. Anyone who uses computers knows they don’t always work perfectly. Bugs are common, and no software is fully tested.
This brings us to a key flaw: since 1999, courts have assumed that machines function properly. This means they view computer-generated information as reliable by default. Marshall highlighted that in the Post Office case, defendants had to explain their issues with the Horizon system, but they could only point to the problems they faced, not fully detail them.
The automatic acceptance of computer evidence in that case was itself an injustice. As my colleague Baroness Kidron said, anyone familiar with programming understands that bugs exist in every system. We all know that updating software often involves fixing issues that weren’t caught before.
Looking at software contracts, it’s clear—most contain disclaimers stating they don’t guarantee uninterrupted or error-free functioning.
It’s been over five years since Lord Justice Fraser ruled that accepting computer evidence without question in the Horizon case was unjust. The responsibility to prove the computer’s unreliability fell on those without access while the Post Office, having the system through Fujitsu, didn’t have to disclose any flaws.
It’s crucial to stress that the Data Bill—or any law—shouldn’t dictate that computer evidence be automatically accepted in court. That judgment should stay with the courts in civil cases and with juries in criminal ones. If the evidence is admitted, it must undergo the usual scrutiny.
In response, Baroness Margaret Jones, the government’s minister for the future digital economy, acknowledged the need to prevent future miscarriages of justice and said they are actively considering the issue, promising to update us in the new year. And here we are—it’s a new year, and we’re all eager to see what they will announce.