Breach of duty - Common practice and its relevance

Learning Outcomes

This article examines breach of duty in negligence and the relevance of common practice, Bolam and Bolitho, including:

• The operation of the objective standard of care and how common practice informs (but does not determine) what is reasonable in the circumstances
• Evidential weight of industry standards, guidance and custom, and circumstances in which courts depart from them
• The Bolam principle in professional negligence and what counts as a “responsible body” of opinion
• Logical scrutiny of expert evidence under the Bolitho qualification, and rejection of professional opinion lacking a logical basis
• Limits of Bolam in consent cases and the effect of Montgomery on pre‑treatment disclosure of material risks
• Interplay of common practice with key breach factors: the likelihood of harm, seriousness of potential injury, cost and practicality of precautions, social utility of the activity, and the state of knowledge at the time
• SQE1‑style problem scenarios involving compliance with, departure from, or reliance on common practice, and clear reasoning on breach of duty

SQE1 Syllabus

For SQE1, you are required to understand how breach of duty is established in negligence, including the significance and limits of common practice, with a focus on the following syllabus points:

• the objective standard of care and the reasonable person test
• the evidential value of common practice and industry standards
• the Bolam principle for professional negligence
• the Bolitho qualification and judicial scrutiny of professional opinion
• how courts balance common practice with the legal standard of care
• how “other relevant factors” affect breach: likelihood and gravity of harm, cost and practicality of precautions, social value of the activity, and the state of knowledge at the time

Test Your Knowledge

Attempt these questions before reading this article. If you find some difficult or cannot remember the answers, remember to look more closely at that area during your revision.

1. What is the evidential significance of a defendant complying with common industry practice in a negligence claim?
2. Under what circumstances can a court reject a responsible body of professional opinion when applying the Bolam test?
3. True or false? If a defendant follows common practice, they can never be found in breach of duty.
4. Which case established that professional opinion must be capable of withstanding logical analysis?

Introduction

When considering breach of duty in negligence, the court must decide if the defendant’s conduct fell below the standard of care expected of a reasonable person in the circumstances. One important factor is whether the defendant followed common practice or industry standards. However, compliance with common practice is not conclusive. This article explains how courts treat common practice, the Bolam and Bolitho principles, and the limits of relying on industry norms.

The Objective Standard and Common Practice

The standard of care in negligence is objective. The defendant is compared to a hypothetical reasonable person in the same situation.

Key Term: standard of care
The level of caution and skill expected from a reasonable person in the defendant’s position.

“Reasonableness” is assessed in the round. Common practice can indicate what careful people ordinarily do and therefore provide a useful benchmark. Equally, it may reveal routines that have become embedded for reasons of convenience, custom, or cost rather than safety. The court’s task is to decide whether adherence to the practice aligns with what a reasonable person would do, given:

• the magnitude of the risk (probability and potential gravity of harm)
• the cost, practicality, and efficacy of precautions
• the social utility of the activity
• the state of knowledge at the time of the alleged breach (not with hindsight)

When assessing breach, courts often consider what is commonly done in the relevant field. If the defendant acted in line with general practice, this is strong evidence that they were not negligent. However, it is not a complete defence. A practice may be widespread yet still unreasonable in light of foreseeable risks or new information. Courts have repeatedly emphasised that it is the standard of reasonable care, not the standard of average care, that the law applies.

Key Term: common practice
The usual or accepted way of doing things in a particular trade, profession, or industry.

Common Practice as Evidence—Not a Defence

Courts treat common practice as persuasive but not decisive. If most people in the industry act in a certain way, it suggests that the conduct is reasonable. But if the practice itself is careless or outdated, following it will not excuse a defendant from liability.

A defendant who can show compliance with a reputable code of practice, professional guidance, or widely adopted procedure will have credible evidence of reasonableness. Yet courts can and do probe:

• whether the guidance fits the facts (a guideline may be sound in general but inapt in the particular scenario)
• whether safer low‑cost precautions were available and practical
• whether the practice has been overtaken by advances in knowledge or technology
• whether the practice adequately addresses the foreseeable seriousness of potential injury

Evidence that a practice is long‑standing or industry‑wide is persuasive, but the legal standard remains objectively reasonable care. For example:

• Likelihood and gravity of harm: The more probable the harm and the more serious its consequences, the more the court expects by way of precautions, beyond “what is usually done”.
• Cost and practicality: Where effective, low‑burden precautions exist, failure to adopt them can be unreasonable even if many others also omit them.
• State of knowledge: Conduct is judged by the knowledge reasonably available at the time, not subsequent discoveries. Practices can become negligent when new risks or countermeasures become known.

Key Term: breach of duty
A failure to meet the standard of care required by law, resulting in a risk of harm to others.

Worked Example 1.1

A warehouse owner stores chemicals in open containers, as is standard in the industry. A fire breaks out, causing toxic fumes to escape and injure neighbours. Can the owner rely on common practice to avoid liability?

Answer:
The owner’s compliance with industry practice is evidence that they acted reasonably. However, if the court finds that the practice is unsafe and a reasonable person would have used safer storage, the owner may still be found in breach of duty.

The Bolam Principle: Professional Negligence

For professionals, the standard of care is that of a reasonable person with the same skill or proficiency. The Bolam test states that a professional is not negligent if they act in accordance with a practice accepted as proper by a responsible body of professionals in that field.

Key Term: Bolam principle
A professional is not negligent if their actions are supported by a responsible body of professional opinion, even if others disagree.

Two points are important for SQE1:

• “Responsible body” does not mean a numerical majority. There can be two respectable schools of thought; either may set a defensible standard of care.
• The body must be competent, impartial, and rooted in the realities of practice, not a fringe view.

Bolam applies across professions—most often in clinical negligence, but also to other skilled callings—because courts accept that professional judgment, training, and risk-balancing are fact‑sensitive.

Worked Example 1.2

A doctor chooses not to warn a patient of a rare risk associated with a procedure. Some doctors would have warned, but a responsible body of doctors would not. Is the doctor negligent?

Answer:
Under the Bolam principle, the doctor is not negligent if their approach is supported by a responsible body of medical opinion.

The Bolitho Qualification: Logical Analysis

The Bolam principle is not absolute. In Bolitho v City and Hackney Health Authority, the House of Lords held that the court is not bound to accept professional opinion if it is not capable of withstanding logical analysis.

Key Term: Bolitho qualification
The court may reject a responsible body of professional opinion if it is unreasonable or illogical.

This means judges are not passive in the face of conflicting expert views. They examine whether the proffered body of opinion:

• addresses the risks and benefits in a reasoned way
• is consistent with the evidence and the state of knowledge at the time
• justifies why the proposed course was reasonable in the circumstances

Key Term: responsible body of opinion
A group of professionals whose views are considered reasonable and competent in the field.

Bolitho scrutiny is not about replacing professional judgment with a judicial opinion; it is about ensuring that professional judgment meets a baseline of rationality. The qualification is used sparingly, but it ensures that unsafe customs or poorly reasoned practices do not shield negligent conduct.

Worked Example 1.3

An engineer follows a widely accepted method for building a bridge, but the method ignores recent safety research. A collapse occurs. Can the court find the engineer negligent despite following common practice?

Answer:
Yes. If the court finds that the common method is illogical or unsafe in light of current knowledge, it can reject the responsible body of opinion and find the engineer in breach of duty.

Worked Example 1.4

A consultant surgeon follows a customary practice not to give a detailed warning about a 1–2% risk of serious nerve damage before spinal surgery. The patient suffers that complication and alleges inadequate warning.

Answer:
Even if a responsible body would not have warned, the claim can still succeed. The modern duty to disclose material risks is governed by patient autonomy (Montgomery), not Bolam. If a reasonable person in the patient’s position would likely attach significance to the risk, or the doctor should reasonably be aware that this particular patient would, the risk should be disclosed. Common professional practice cannot dilute this legal requirement.

When Common Practice Will Not Excuse Negligence

Courts may find a defendant liable even if they followed common practice where:

• the practice is clearly unsafe or outdated
• new risks or knowledge have emerged
• the practice fails to address foreseeable dangers
• low‑cost, practical precautions were available and proportionate to the risk
• adherence to practice ignored the heightened seriousness of potential injury in the circumstances
• the activity’s social utility did not justify omitting reasonable safeguards

Common practice sits within a broader breach analysis. In applying the reasonable person standard, courts weigh:

• Likelihood of harm: Where the probability of injury is greater, more care is required.
• Seriousness of potential injury: Even low‑probability risks may demand precautions if the possible harm is grave (for example, eye protection where loss of sight would be catastrophic).
• Cost and practicality: Reasonable care does not require eliminating every risk, but it expects proportionate, effective measures where feasible.
• State of knowledge: Conduct is judged by the knowledge reasonably available when the decision was made. It is not negligent to fail to guard against risks not reasonably appreciated at the time, but it can be negligent to ignore known hazards or newly available safeguards.
• Social utility: Emergency or socially valuable activities may justify taking some risks, but they do not excuse avoidable hazards.

The interplay with statute and policy is also relevant. The Compensation Act 2006 confirms that, when determining whether a defendant took reasonable care, courts may consider whether requiring further precautions would prevent a desirable activity from taking place. This does not lower the standard of care; it ensures context is part of the reasonableness balance.

Exam Warning Do not assume that following common practice is a complete defence. Courts will consider whether the practice itself is reasonable and up to date.

Worked Example 1.5

A light‑industrial workshop stores solvents under benches with lids loosely fitted. That is how most similar workshops operate locally. A small spill ignites and a worker suffers severe burns. The defendant argues that everyone in the sector does the same and that proper ventilated cabinets are expensive.

Answer:
The custom is persuasive but not conclusive. If reasonably affordable, effective safety cabinets or simple containment measures were available, and the foreseeable risk and potential gravity of burns were significant, a court may find breach despite the local custom. The key questions are proportionality of precautions and state of knowledge about solvent fire risks—common practice is only one factor.

Summary Table: Common Practice and Breach of Duty

Applying the Principles to Typical Fact Patterns

Two recurring themes appear in problem questions:

• Compliance with guidance or custom that omits a simple, effective precaution. The court asks whether, in light of the risk and available measures, a reasonable person would have gone further than the custom. If the risk is serious and the measure is practical (for example, inexpensive guards, goggles, signage, or storage), failure to adopt it may be negligent.
• Reliance on expert opinion that does not engage with risk/benefit in a reasoned way. Even where experts disagree, a court can reject an opinion that fails logical scrutiny. For example, where expert support is based on outdated data or fails to consider a known contraindication for the specific patient or site conditions for a structure, the opinion may not withstand Bolitho analysis.

Equally, defendants who depart from custom can still avoid liability if they show that their approach was objectively careful. Reasonable care does not require slavish adherence to custom. Innovation that demonstrably manages risk effectively can be reasonable even if unusual.

Integrating Other Breach Factors with Common Practice

Because common practice is a piece of the broader breach puzzle, it often interacts with the classic breach factors:

• Likelihood of harm: In contexts where harm is statistically rare, compliance with careful practice may suffice. Where it is more likely (for example, foreseeably frequent projectiles on a site), stricter precautions may be expected regardless of custom.
• Seriousness of harm: Where consequences could be devastating (loss of sight, paralysis), courts expect defendants to account for that gravity—custom may not be enough if a modest extra step would materially reduce the risk.
• Cost/practicability: Courts do not expect defendants to shut down operations (unless that is the only reasonable choice where risks are intolerable). But if a measure is low‑cost and effective, a failure to adopt it is harder to justify by pointing to custom alone.
• Social utility: In emergencies or urgent rescue, conduct is assessed in that context. However, social value rarely excuses ignoring planned, straightforward protections in routine operations.
• State of knowledge: Compliance with custom aligns with reasonableness if the custom tracks what is known at the time. But once new hazards or solutions emerge, custom should change. An unchanged custom can drift below the legal standard if it fails to reflect reasonable contemporary knowledge.

Professional Practice: Beyond Treatment Decisions

While Bolam is central to clinical treatment decisions, its reach is broader: engineering, law, accountancy, architecture, and other skilled professions. Across these, responsible bodies of opinion may exist on design tolerances, auditing steps, case handling, or safety margins. The key in every field is whether the professional decision stands up to logical analysis. If a professional cannot explain why the risks were acceptable given the alternatives, a court may conclude that the responsible body’s view is not, in truth, responsible.

Bolam does not govern all aspects of professional‑client relationships. In clinical practice, Montgomery establishes that risk disclosure is determined by materiality to the patient, not by what a respectable body of doctors would have said. This is an important limit to arguments based on custom when the alleged breach concerns advice and consent rather than technical treatment.

Practical Guidance for Analysis

When you encounter a scenario in which a defendant relies on common practice:

• Identify the practice and who follows it (local custom, national guidance, professional body recommendations).
• Ask whether the practice is demonstrably safe in light of the risks, or whether it appears to prioritise convenience or cost over safety.
• Consider whether low‑cost, practical steps could materially reduce the risk.
• Evaluate whether the defendant’s decision reflects the state of knowledge at the time.
• In professional cases, ask whether a responsible body supports the conduct and whether that view withstands Bolitho scrutiny.
• Check for domains where Bolam does not apply (for example, informed consent to treatment in Montgomery).

A structured analysis shows why common practice may support reasonableness yet still yield to a finding of breach when the broader factors demand more.

Key Point Checklist

This article has covered the following key knowledge points:

• The standard of care is objective and based on the reasonable person.
• Common practice is persuasive evidence but not a defence if the practice is unsafe, outdated, or does not reflect contemporary knowledge.
• Courts integrate common practice with classic breach factors: likelihood and gravity of harm, cost and practicality of precautions, social utility, and the contemporaneous state of knowledge.
• The Bolam principle protects professionals who follow a responsible body of opinion, but “responsible” is qualitative, not a headcount.
• The Bolitho qualification allows courts to reject illogical or poorly reasoned professional opinion.
• In clinical law, Montgomery limits reliance on Bolam for disclosure of risks and alternative treatments: materiality to the patient governs.
• Defendants may be liable even where industry standards are met if reasonable care required more; equally, careful departures from custom can be non‑negligent.

Key Terms and Concepts

• standard of care
• common practice
• breach of duty
• Bolam principle
• Bolitho qualification
• responsible body of opinion