LEGAL ENGLISH · C1 · 50 min

The Computer Was Never Wrong

For sixteen years the law assumed the accounting system was working properly. Hundreds of people were prosecuted because they could not prove otherwise — and they had no way of proving it.

Today: you'll work through what is generally regarded as the most widespread miscarriage of justice in British legal history — and you'll sharpen the structures that make responsibility disappear from a sentence: it was held that, the shortfall was attributed to, the system is presumed to have been operating correctly.

A note on this case. Real people were bankrupted, imprisoned and shunned in their own villages, and a public inquiry has found that a number took their own lives. The facts are stated plainly because the language point only matters if the consequences stay in view.

Discuss:

When a system in your organisation says a person is wrong, who is believed first — and what would it take to reverse that?
Have you ever had to disprove something a computer asserted about you? What evidence were you actually able to get hold of?
Where in your sector does one party hold all the data, and the other party carries all the liability?

The vocabulary of this case

Ten items. Work through the four activities — say your answer out loud before you reveal it.

A · What do they mean here? Work it out from the context

1. The prosecution never had to prove that the accounting system was working correctly. The law started from the position that it was, and left the defendant to show otherwise — a presumption in favour of the machine.

a presumption (n) — a starting position the law takes as established unless displaced. Two kinds: rebuttable (it can be displaced by evidence) and irrebuttable (it cannot). Verb to presume; the phrase you will meet in statutes is "shall be presumed unless the contrary is proved".

2. Bugs in the system had been recorded internally. Engineers could alter branch accounts remotely. None of this reached the people on trial, because the prosecutor did not hand over the material it held — a failure of disclosure.

disclosure (n) — the duty to give the other side material relevant to the case, including material that damages your own. US term: discovery. Collocations: the duty of disclosure, unused material, to disclose, and the failure itself: non-disclosure. In criminal proceedings this duty is the single most common source of quashed convictions.

3. When the convictions finally reached the Court of Appeal, the objection was not only that the evidence was unreliable. It was that bringing the prosecutions at all, in those circumstances, was so unfair that the courts should never have entertained them — an abuse of process.

an abuse of process (n) — the use of legal proceedings in a way that is unfair or improper, entitling a court to stay or strike them out regardless of the merits. Two limbs in criminal law: the accused cannot have a fair trial, or it would offend the court's sense of justice to try them at all. The second limb is the graver finding.

B · Which term means…?

Three terms: to quash · to exonerate · redress. Say the right one, then reveal.

1. Which verb means for a higher court to set aside a conviction so that it no longer stands?

to quash (v) — the convictions were quashed. In this saga the word acquired an unusual companion: convictions were also quashed by statute, which is not how the word normally works. Related: to overturn, to set aside, to vacate (US).

2. Which verb means to clear someone officially of blame or of an accusation?

to exonerate (v) — noun exoneration. Note the difference from acquit: an acquittal says the case was not proved; exoneration says the person was not to blame. Many of those affected have said, in exactly these terms, that quashing was not the same as being believed.

3. Which noun means the putting right of a wrong — compensation and remedy taken together?

redress (n, uncountable) — to seek redress, a redress scheme, to obtain redress. Broader than compensation (money) and than a remedy (what a court can order). It is the word the schemes in this case were named after, and the word most contested afterwards.

C · Choose the meaning — a / b / c

1. The organisation that ran the accounting system also brought the criminal charges itself, without going through the state prosecutor. This is a private prosecution. It means…
(a) a trial held in private, without the press (b) a criminal case brought by a private body or individual rather than by the state prosecuting authority (c) a civil claim for money

(b) — a private prosecution, long available in England and Wales and used by a range of bodies. The structural problem it raises here is plain once stated: the prosecutor was also the alleged victim, the owner of the evidence, and the contractual counterparty of the accused.

2. Hundreds of claimants with the same complaint eventually sued together in one managed set of proceedings, under a court order grouping their claims. This is group litigation. Its practical effect is that…
(a) each claimant must still fund a separate trial (b) common issues are decided once, for everyone in the group, at a cost no individual could have borne alone (c) the claims are decided by a regulator instead of a court

(b) — group litigation (in England, under a Group Litigation Order; the nearest US relative is the class action). It is how individually unaffordable claims become viable — and, as this case shows in the bleakest way, how the cost of funding such litigation can consume most of what is won.

D · Collocation & word building

1. Complete the standard phrase for what happens when an innocent person is convicted: a miscarriage of ___. Then give the two verbs most often used with it — one for what a system does, one for what a court does about it.

a miscarriage of justice. Verbs: a system causes or gives rise to one; a court corrects or remedies it (and quashes the conviction). Note the plural: miscarriages of justice — the "s" goes on the first noun, which is where writers slip.

2. A presumption that can be displaced by evidence is described by one adjective: a ___ presumption. Complete it, give the verb it comes from, and then give the fixed phrase a statute uses to signal that the presumption can be displaced.

a rebuttable presumption, from the verb to rebut (noun rebuttal). The statutory phrase: "unless the contrary is proved" — or "in the absence of evidence to the contrary". Keep the pair: a presumption is only as fair as the losing party's ability to rebut it.

Now use them — out loud

Before we read:

Using presumption, rebuttable, disclosure and abuse of process, predict how a fair-looking rule of evidence could produce hundreds of wrongful convictions without anyone breaking it.
Which of these terms would you use in a submission, which to a client, and which to a journalist? Sort them out loud, and give the plainest version of abuse of process.

The case, in three parts

Read each part. After it, there's a quick check (answer from memory first), then one question to discuss.

Part 1 — The shortfalls

From 1999 the Post Office began rolling out a new computerised accounting system, built by a large IT contractor, across some fourteen thousand branches. The people running those branches were not employees. Sub-postmasters were self-employed, they had invested their savings in the business, and their contracts made them personally liable for any shortfall in the branch accounts.

Almost immediately, shortfalls appeared. A branch would balance one evening and be thousands of pounds short the next, with no cash missing from the safe. Sub-postmasters rang the helpline and were told, again and again, that they were the only person reporting the problem. Some made up the difference from their own money, month after month, hoping it would resolve. Some mortgaged houses. When the sums became too large to cover, the Post Office prosecuted them — for theft, for fraud, for false accounting.

It did so itself. In England and Wales a private body may bring a criminal prosecution, and the Post Office had done so for generations. So the organisation that owned the system, held all the data about it, and was the contractual counterparty of every accused person was also the prosecutor. Over roughly sixteen years, in the region of seven hundred sub-postmasters were prosecuted on evidence from those accounts. People went to prison. Marriages ended. In villages where the sub-postmaster is a person everyone knows, families were treated as thieves. The public inquiry that followed found that a number of those affected took their own lives.

Quick check — from memory, then reveal:

1. Why did the contractual position of sub-postmasters matter so much?

2. What made the Post Office's role in the prosecutions structurally unusual?

1. They were self-employed and personally liable for shortfalls, so an error in the accounts became their own debt immediately — which is why so many paid the missing sums out of their own money before any prosecution began.

2. The Post Office prosecuted privately. It was simultaneously the alleged victim, the owner and controller of the evidence, the other party to the contract, and the prosecutor — four roles that a state prosecution keeps apart.

Discuss:

Each sub-postmaster was told they were the only one. Where in your organisation would a pattern of individual complaints fail to be seen as a pattern — and who would have to notice?

Part 2 — The presumption that did the damage

The legal mechanism at the centre of this is quiet, technical, and was designed with good intentions. English law had once required a party relying on computer evidence to show that the machine was operating properly. That requirement was repealed at the end of the 1990s, on the reasoning that it had become an empty formality in an age when computers were everywhere. What replaced it was the ordinary common-law presumption that a mechanical instrument was working correctly unless there was evidence to the contrary.

Read that sentence again from the position of a sub-postmaster in a village branch. The system is presumed to be working. To displace the presumption you need evidence that it was not. That evidence consists of error logs, defect records, and knowledge of whether anyone can alter branch data from outside — all of which is held by the organisation prosecuting you, and none of which you have ever seen. The presumption is formally rebuttable and practically irrebuttable, and the difference between those two words is the whole scandal.

What the disclosure would have shown, when it finally came, was that known defects existed and had been recorded; that shortfalls could be generated by the system itself; and that the contractor could alter branch accounts remotely, without the sub-postmaster's knowledge or consent. That last point had been denied in court. Sub-postmasters who said in the witness box that something must have been done to their accounts from elsewhere were telling the truth, and were not believed, because the only people who could confirm it were on the other side.

Quick check — from memory, then reveal:

1. What changed in the law about computer evidence, and why was the change made?

2. Explain the gap between a formally rebuttable presumption and a practically irrebuttable one.

1. The requirement to prove a computer was working properly was repealed in the late 1990s as an outdated formality, leaving the ordinary presumption that a mechanical instrument works correctly unless there is evidence to the contrary.

2. In form, the defendant may rebut it with evidence. In practice, all the evidence capable of rebutting it — error logs, defect records, remote access records — was held by the prosecuting organisation and was not disclosed. A right you cannot exercise is not a protection.

Discuss:

A rule was repealed because it had become a formality, and its removal caused this. What "pointless" control in your own organisation might be doing quiet work nobody has measured?

Part 3 — Bates, Fraser, and an Act of Parliament

The turn came from one former sub-postmaster, Alan Bates, who was not prosecuted but was removed from his branch, and who spent years assembling the others into an organised group. In 2019 their group claim came before Mr Justice Fraser in the High Court. In a series of long, unusually direct judgments he found the Post Office's contractual conduct oppressive and held that the Horizon system had not been remotely as robust as had been claimed. The Post Office attempted to have him removed from the case; that application failed. The claim settled at the end of 2019 for around £58 million — of which, after the cost of funding the litigation, roughly £12 million reached the claimants themselves, spread across more than five hundred people.

In 2021 the Court of Appeal quashed the first large group of convictions, holding that the prosecutions had been an affront to the conscience of the court. More followed. Then, in January 2024, a television drama put the story in front of the public over four evenings, and the politics changed in about a week. Parliament passed legislation the following year that quashed convictions wholesale, by statute — an extraordinary step, and one constitutional lawyers argued about at the time, because it is not the ordinary business of a legislature to decide who was innocent.

The public inquiry under Sir Wyn Williams reported in 2025 on the human cost, setting out the bankruptcies, the imprisonments, the illnesses, and the deaths. The compensation schemes continue, and are still criticised by claimants for their slowness and for requiring people who were wrongly prosecuted to prove their losses in detail, years later, to the organisation that prosecuted them. That last point is the case in miniature: at every stage, the burden sat with the person who had the least ability to discharge it.

Quick check — from memory, then reveal:

1. What did the High Court find in 2019, and what happened to the money?

2. Why was quashing convictions by Act of Parliament constitutionally unusual?

1. That the Post Office's conduct had been oppressive and that the system was not robust. The claim settled for around £58 million, but litigation funding costs absorbed most of it, leaving roughly £12 million for more than five hundred claimants.

2. Because deciding whether a particular person was rightly convicted is a judicial function. Parliament quashing convictions in bulk crosses that line — defensible here on the ground that the courts would have taken years, but not a precedent anyone wants used casually.

Discuss:

It took a television drama to move the government, twenty years after the first complaints and five years after a judge had found the system unreliable. What does that say about how evidence actually travels?

Passives & presumption

This is the grammar of institutions. The passive lets you state what happened without stating who did it; presumption language lets you state what will be taken as true without proving it. Both are indispensable in legal writing, and both are how responsibility quietly leaves a document.

The agentless passive — the workhorse:
• "The shortfall was attributed to the sub-postmaster." — by whom? The sentence does not say, and does not have to.
• "It was held that the presumption applied." · "The material was not disclosed." · "Concerns had been raised internally."
Legitimate uses: the actor is obvious, unknown, or genuinely irrelevant; or the object is the real subject of the sentence. Illegitimate use: the actor is known and inconvenient.

Presumption verbs — the language of what is taken as true:
• is presumed — "The system is presumed to be operating correctly."
• is deemed — a legal fiction: it may not be true, and the law treats it as true anyway. "Notice is deemed to have been served on the second business day."
• is taken to be / shall be regarded as — softer variants of the same operation.
• The escape hatch, which is the most important part of the clause: unless the contrary is proved · in the absence of evidence to the contrary · until rebutted.

Two structures worth having exactly right:
• The passive perfect infinitive: "The system is presumed to have been functioning correctly at the material time." · "The notice is deemed to have been received." This is how a present rule reaches back to a past state, and it is everywhere in evidence law.
• Reporting passives, for attributing without adopting: "It is said that…" · "It has been suggested that…" · "The defects are understood to have been known internally." You report the claim and do not endorse it — genuinely useful, and also the standard way an organisation acknowledges something without admitting it.

The reverse skill, and the point of this whole lesson: knowing when to put the agent back. "Errors were made in the branch accounts" and "our contractor altered branch accounts remotely without telling the sub-postmaster" describe the same events. The second is a sentence somebody has to own. When you are writing an apology, a disclosure statement, or a finding, the test is simple: read it back and ask who did it. If the sentence cannot answer, decide whether that is honesty or shelter.

1. Make it a presumption

A local authority is drafting rules for its automatic parking-enforcement cameras. Complete each gap — one to four words.

1. The camera is treated as accurate unless someone shows otherwise. → "The camera to have been operating correctly at the time of the alleged contravention."

2. And here is the escape hatch. → "… the contrary is proved."

3. A notice posted on Monday counts as arriving on Wednesday, whether it did or not. → "A notice served on the second working day after posting."

4. Nobody is named as the person who checks the machines. → "Calibration records at six-monthly intervals." (agentless passive)

1. is presumed / shall be presumed 2. unless 3. is deemed to have been 4. are reviewed / shall be reviewed

Sentence 4 is the one to notice. It states that a check happens without stating that anybody is responsible for doing it — and that is precisely the shape of a control that turns out, years later, never to have been performed.

2. Put the agent back

A bank's fraud-detection system wrongly froze several hundred customer accounts. Rewrite each institutional sentence so that it names who acted. Write only the missing words.

1. "Accounts were suspended in error." → "Our fraud team four hundred accounts in error."

2. "It has been acknowledged that the model was not retested after the update." → "We that we did not retest the model after the update."

3. "Concerns had been raised internally." → "Two analysts concerns in writing in March, and acted on them."

4. "Customers were not informed until the matter was resolved." → "We customers for eleven days."

1. suspended 2. accept / acknowledge 3. raised · nobody (or no one) 4. did not tell / did not inform

Read the two columns side by side and time how long each takes to say. The passive version is shorter, calmer, and answers no question a customer is actually asking.

3. The disclosure statement — complete the passage

An examination board's plagiarism-detection software has flagged students wrongly for two years. You are drafting the statement. It must be formal without hiding. Complete it, then read it aloud.

"Between 2023 and 2025, the detection system to be reliable, and its output as sufficient evidence of misconduct without further corroboration. That approach was wrong, and it was ours. Defect reports internally in 2024; they were not passed to the panels deciding individual cases, and no one to pass them on. Where a finding on that output alone, we are setting it aside. Students will not to prove that the software was wrong; we accept that they were never in a position to do so, because the records by us."

was presumed · was treated · were raised · was required (or was responsible) · was based · be required / be asked · were held

Notice the hinge: "That approach was wrong, and it was ours." One short active sentence in the middle of a formal passage does more than the whole paragraph around it. The passives set out the mechanism; the active sentence accepts the responsibility.

Take these into the Speak tab: you will be explaining a systemic failure in two registers — the one that protects the institution, and the one that tells the truth.

Going deeper

A note before we argue: the events are summarised here, figures are rounded, inquiries and compensation schemes are continuing, and legal systems differ — this is material for discussion and for language, not legal advice on any real matter.

What the case actually tests. The comfortable reading is that an organisation behaved appallingly and has been found out. That reading is available, and the inquiry has supplied plenty of material for it. But it lets everybody else off, and the more useful reading is structural. No single person designed this. A presumption was adopted for sensible reasons. A prosecution power existed for historical reasons. A contract allocated shortfalls to the person nearest the till, which is ordinary commercial practice. A helpline told each caller they were the only one, which was what the script said. Each element was defensible on its own; combined, they made it impossible for the truth to travel upwards, and then made it impossible for the people affected to prove it. Ask of your own organisation not "would we do something like this?" but "which of our defensible individual rules would combine like that?"

The second question is about evidential presumptions in general, and it is now urgent. The presumption of proper functioning was never absurd: courts cannot re-prove the reliability of every machine in every case, and the requirement it replaced had genuinely become a formality. The failure was not the presumption but the asymmetry — one party held all the evidence capable of rebutting it. That asymmetry is not going away. It is the ordinary condition of every dispute involving an algorithmic decision, a fraud model, a telematics box, a content-moderation system. The question the case leaves for the next decade is what a fair presumption looks like when only one side can see inside the machine.

And the third is about remedy, where the story is least satisfying. Convictions were quashed; a settlement was reached that litigation funding largely consumed; Parliament exonerated people in bulk because the courts would have taken a decade; compensation schemes still ask people who were wrongly prosecuted to evidence their losses to the body that prosecuted them. Something was put right. It was slow, it arrived after a television programme rather than after a judgment, and the burden stayed, at every stage, on the people with the least capacity to carry it.

Talk it through:

Argue in favour of the presumption of proper functioning — a court cannot audit every system, and without it litigation becomes unworkable. Then say what condition you would attach to it, and who would enforce that condition.
Should a private body ever be able to prosecute people over evidence it alone controls? If not, what is lost by removing the power?
Parliament quashed convictions by statute because the courts were too slow. Was that justice, or a precedent you would rather not have? Argue the side you find harder.
Take one automated system your organisation relies on to make decisions about people. If someone said tomorrow that it was wrong about them, what could they get hold of — and how long would it take?

Speak

All of it out loud, against the clock. Three registers: setting out a systemic failure, defending a rule you may not like, and saying the same facts to four rooms with very different interests.

Useful language: it was held that… · the system is presumed to have been operating correctly · unless the contrary is proved · notice is deemed to have been served · concerns had been raised · and to break the pattern: we did this, and it was wrong.

Time remaining: 4:00

Task A · Explain what happened (4 minutes)

Present this to someone who has never heard of it, and make the mechanism as clear as the outrage. Structure it: the system and the contracts → the shortfalls and the helpline → private prosecution → the presumption and why it could not be rebutted → what disclosure eventually showed → the group claim, the appeals, the statute, the inquiry.

Finish with one sentence naming the structural fault rather than the villain. Use at least five key terms (presumption, rebuttable, disclosure, abuse of process, quash, exonerate, redress, private prosecution, group litigation, miscarriage of justice).

Task B · Argue the difficult side (4 minutes)

Defend the presumption of proper functioning to a hostile audience. Your case: courts cannot re-prove every machine in every case; the rule it replaced had become an empty ritual; hundreds of ordinary prosecutions depend on machine output being usable; and the real failure here was disclosure, not presumption.

Concede the asymmetry honestly, and say what you would require in exchange. Then do it again in ninety seconds.

Task C · Four rooms, one failure (4 minutes)

Take one systemic failure in which an organisation's system was wrong about individuals. Account for it four ways, one minute each. The facts must be identical in all four; only the register changes.

To the board: the mechanism, the exposure, and which control should have caught it.
To the people affected: active sentences, named actors, no institutional passives — and an apology that does not contain the word "if".
To a regulator or inquiry: formal register, presumption and disclosure language, precise about dates and about what was known when.
To your own staff: what changes on Monday, and how someone raises the next one without being told they are the only one.

Prefer not to use anything of your own? Take one of these instead:

A bank whose fraud model froze several hundred accounts wrongly.
A benefits agency whose overpayment algorithm generated debts that did not exist.
An exam board whose plagiarism software flagged honest students for two years.
A logistics firm whose telematics wrongly recorded drivers as speeding, leading to dismissals.

To finish — the harder questions

When only one side can see inside the machine, where should the burden of proof sit? Give a rule you would actually be willing to draft, and say what it costs.
Every element here was individually defensible. Name two rules in your own organisation that are defensible alone and dangerous together.
It took a television drama to move the state, five years after a judge had found the system unreliable. What does that tell you about where to take evidence that nobody is acting on?
Before you go — from memory: describe a failure in one sentence using an agentless passive, then say the same sentence again with the agent named. Then say which version your organisation would publish, and whether you agree with it.