Hindsight bias is the tendency, once an outcome is known, to see it as more predictable than it was at the time. In a clinical negligence claim, breach of duty is judged by what a reasonably competent clinician would have done with the information available when the decision was made, so the court and every expert have to set the outcome aside.
In short: psychology research going back to the 1970s shows that people who are told an outcome overrate how foreseeable it was, and that specialists judge identical care more harshly when the result was severe. English law has guarded against this since at least 1954, when the Court of Appeal refused to judge a 1947 anaesthetic with later knowledge.
The Bolam standard is applied as at the date of treatment, judges warn themselves against being “wise through hindsight”, and a Part 35 expert is expected to reconstruct what was known at each decision point rather than reason backwards from the result. Hindsight can distort an opinion in either direction, so guarding against it is a question of method, not of side.
What Is Hindsight Bias?
Hindsight bias is the way that knowing how events turned out changes a person’s sense of how likely that outcome was beforehand. The psychologist Baruch Fischhoff described it in a 1975 paper in the Journal of Experimental Psychology, calling it “creeping determinism”: once people were told an outcome had happened, they judged it to have been relatively inevitable.
The reader of a set of notes cannot un-know the ending. The warning signs that led to it look clearer than they did at the time, and the reassuring signs that pointed elsewhere fade into the background.
Why Does Hindsight Bias Matter in a Clinical Negligence Claim?
Because every clinical negligence claim starts with a known bad outcome. Nobody commissions a report on an operation that went well. The solicitor, the expert and the judge all read the records already knowing that the wound broke down, the nerve was injured or the diagnosis came late.
There is direct evidence that this changes clinical judgement. In a 1991 study in JAMA, Caplan, Posner and Cheney gave a panel of experienced anaesthetists 21 case summaries, each paired with an identical version in which only the outcome changed, from a mild and reversible injury to a severe and permanent one. The same care was about 30% more likely to be judged substandard when the outcome was severe.
The reviewers were specialists rating care in their own field. That is exactly the position of a medical expert witness.
Is Hindsight Bias the Same as Outcome Bias?
Not quite, although the two usually travel together. Hindsight bias is about foreseeability: after the event, the outcome seems to have been more predictable than it was. Outcome bias is about quality: a decision is judged better or worse depending on how things turned out.
Jonathan Baron and John Hershey demonstrated outcome bias in 1988, using scenarios that included medical decisions made by doctors and by patients. Participants rated the same decision as better reasoned, and the person who made it as more competent, when the outcome was favourable. Asked directly, they said outcomes should not affect the judgement, yet they did.
In a negligence claim the two combine. A complication makes the risk look obvious in retrospect, and makes the decision that came before it look careless.
How Did the Courts First Deal With Hindsight?
The classic statement comes from Roe v Minister of Health [1954] 2 QB 66. In 1947 patients were left paralysed after spinal anaesthetics because the anaesthetic had been contaminated with phenol through cracks in the glass ampoules too fine to see. The risk was not recognised at the time, and the claims failed.
Denning LJ warned against looking at the 1947 accident with “1954 spectacles”. The question was what a careful anaesthetist could reasonably have known and done in 1947, not what everyone knew by the time of the trial.
How Is Breach of Duty Judged Without Hindsight?
By applying the standard of care as it stood at the date of treatment. Under the Bolam test, a clinician is not negligent if they acted in accordance with a practice accepted as proper by a responsible body of medical opinion, and since Bolitho in 1997 that opinion also has to withstand logical analysis. Both questions are asked from the clinician’s position at the time.
In practice the court looks at four things.
- What the clinician knew, or should have known, from the history, examination and results available then.
- What guidance and accepted practice were in force on that date, rather than later revisions.
- What options were reasonably open, and whether the choice made fell within the range a responsible body of practitioners would support.
- Whether the reasoning behind the decision holds together on its own terms.
The outcome is relevant to causation and to the value of the claim. It is not, on its own, evidence that the earlier decision was wrong.
What Did the Court Say in C v North Cumbria?
C v North Cumbria University Hospitals NHS Trust [2014] EWHC 61 (QB) sets out guidance on how a court weighs competing expert evidence, and it addresses hindsight directly. The claim concerned whether a midwife was negligent in giving a second dose of Prostin to induce labour. It failed.
Green J listed the factors for assessing an expert’s opinion and said that by far the most important is its logic, tested against the contemporaneous clinical notes and the rest of the evidence at trial. On the second dose he said: “I must be very wary of being wise through hindsight.” He added that the fact the dose turned out to be catastrophic was not relevant.
Where Does Hindsight Creep Into a Plastic Surgery Claim?
Wherever a later finding is read back into an earlier record. Three patterns come up in plastic, reconstructive and hand surgery work.
- A hand laceration closed in an emergency department and later found, at exploration, to involve a divided tendon or digital nerve. Knowing the structure was cut makes any documented examination look inadequate. The question is what a competent examination of that wound, at that time, would have shown and recorded.
- A flap or wound that failed after surgery. Once the failure is known, every earlier observation of colour or swelling reads like a missed warning. The question is whether the observations recorded at each check should have prompted a competent clinician to act at that point.
- A cosmetic result the patient is unhappy with, such as a widened or raised scar. A poor scar does not by itself show poor technique, because healing also depends on the patient. The question is whether the surgery and aftercare fell below a responsible standard.
In each case the expert works forwards through the records in time order, rather than backwards from the result.
How Should a Part 35 Report Deal With Hindsight?
Openly. Practice Direction 35 says expert evidence should be the independent product of the expert, uninfluenced by the pressures of litigation, and where there is a range of opinion the report must summarise it and give reasons for the expert’s own view. A report that handles hindsight well will usually do five things.
- Build a chronology from the contemporaneous records before forming any view.
- Identify each decision point and state what information the clinician had at that moment.
- Apply the guidance and practice in force on that date, and say so where it has since changed.
- Keep the breach question separate from the causation question, so that knowledge of the outcome informs only the second.
- Acknowledge where a responsible body of practitioners would have acted differently from the expert’s own preference.
The rules themselves are summarised on the CPR Part 35 page, and the structure of a report on the medico-legal report page.
Does Hindsight Matter for Causation Too?
Causation asks a different question: what would probably have happened if the care had been competent. The court answers it on the balance of probabilities using all the evidence before it, so knowing how the condition developed is relevant there in a way it is not to breach.
The risk of reasoning backwards does not disappear. An expert who starts from the final outcome and assumes its signs must have been present earlier is reconstructing the past from the ending. The timeline for causation still has to be built from what the records show, not inferred from the result.
Hindsight Cuts Both Ways
Hindsight bias can look like a risk only to clinicians, but it is a risk to the accuracy of any opinion. A severe outcome can make reasonable care look negligent. A good outcome can make a poor decision look sound, which is the other half of the outcome bias research: the same decision was rated better when it turned out well.
That is why avoiding hindsight is part of an expert’s method rather than an argument for either party. Under CPR 35.3 an expert’s duty is to help the court on matters within their expertise, and that duty overrides any obligation to the person who instructed or is paying them. It applies in the same way whichever side, or both sides jointly, gave the instruction.
Questions to Ask When Reviewing an Expert Report
A few questions test whether hindsight has found its way into an expert’s report.
- Does the report set out what was known at each decision point, or only what is known now?
- Are the guidelines cited the versions in force at the date of treatment?
- Does the reasoning on breach still stand if the outcome is covered over?
- Where a decision is criticised, does the expert explain what a competent clinician should have done instead, and why that was apparent at the time?
- Does the report acknowledge a range of reasonable practice where one exists?
Frequently Asked Questions
Is hindsight bias a legal defence? No. It is a reasoning error that courts and experts try to avoid. Whether care was negligent is still decided by applying the standard of care that applied at the time.
Can later medical knowledge ever be used? Yes, on causation and on condition and prognosis, where the court needs the best current understanding of what happened to the patient and what the future holds. On breach, the standard is the accepted practice when the treatment was given.
Does a bad outcome mean the care was negligent? No. Complications can follow competent care. A bad outcome is the reason a case is examined, not proof that the care fell below the standard.
How can an expert show they have avoided hindsight? By working from the contemporaneous records in time order, identifying the information available at each point, and explaining the reasoning so the court can test its logic, the factor Green J described as by far the most important.
Related Reading
- Bolam to Montgomery and how the test for clinical negligence changed
- Why independent clinical opinion matters in medico-legal cases
- Medical records as evidence in a negligence claim
Instructing an Expert on Breach of Duty
Breach of duty in plastic, reconstructive, cosmetic and hand surgery turns on what a competent surgeon would have known and done at the time. Prof. Hindocha prepares CPR Part 35 compliant medico-legal reports in medical negligence claims for claimants and defendants, working from the full records. See how to instruct.
This article is general information about how hindsight is treated in clinical negligence claims in England and Wales. It is not legal advice and it is not clinical advice about any individual case. Anyone considering a claim should take advice from a solicitor on their own circumstances.