Causation — Factual and Legal Causation

1. Introduction

Causation is one of the fundamental requirements for establishing liability in tort, contract, crime, and many statutory claims. It establishes the connection between the wrongful act or omission of a defendant and the harm suffered by the claimant.

It is not enough to show:

"The defendant acted wrongfully."

The claimant generally must also demonstrate:

"The defendant's wrongful conduct caused my legally recognizable loss."

Causation therefore performs a filtering function. It prevents a person from being held liable for every consequence that happens to follow an act.

Causation is commonly divided into two major questions:

Factual causation — Did the defendant's conduct actually cause the harm?

Legal causation — Is the defendant sufficiently connected to the harm that the law should impose liability for it?

A useful formulation is:

Factual causation asks "Did the defendant cause it?"

Legal causation asks "Should the law attribute this consequence to the defendant?"

2. Why Causation Is Necessary

Suppose A negligently leaves a dangerous object on a road.

B later suffers injury.

A claimant must establish more than the existence of A's negligence.

The court may ask:

Would B have been injured without A's conduct?

Did some independent event cause the injury?

Was the injury a foreseeable consequence?

Was the connection too remote?

Did another person's intervening act break the chain?

Did the claimant's own conduct contribute to the harm?

Causation therefore separates wrongful conduct that produces legally attributable harm from wrongful conduct that does not.

3. Causation in Tort Law

In negligence, a claimant generally has to establish:

duty of care;

breach of duty;

factual causation;

legal causation/remoteness;

damage.

Thus:

Duty → Breach → Factual Cause → Legal Cause → Damage

Failure at any necessary stage may defeat the claim.

4. Factual Causation

Meaning

Factual causation asks whether the defendant's conduct was an actual cause of the claimant's injury.

The classic test is the:

"But-for" test

The question is:

But for the defendant's conduct, would the claimant have suffered the injury?

If the answer is no, factual causation is ordinarily established.

If the answer is yes, the defendant's conduct may not be a factual cause.

5. Simple Example of the But-For Test

Suppose a driver negligently runs a red light and hits a pedestrian.

The pedestrian would not have been struck but for the driver's negligent driving.

Therefore:

Negligent driving → collision → injury

The driver's conduct is a factual cause of the injury.

6. Factual Causation in Medical Negligence

Suppose a doctor negligently fails to diagnose a serious disease.

The claimant later dies.

The court must determine:

Would the patient have survived or had a materially better outcome if the doctor had acted properly?

If the patient would have died anyway at substantially the same time, factual causation may be difficult to establish.

This demonstrates why causation is separate from the question of negligence.

A doctor may have acted negligently but nevertheless not be legally responsible for the ultimate injury if the negligence did not cause it.

7. Legal Causation

Even when factual causation exists, liability does not necessarily follow.

Legal causation asks whether the connection between the defendant's conduct and the harm is sufficiently strong for liability to be imposed.

This is sometimes expressed through the concepts of:

remoteness of damage;

foreseeability;

proximate cause;

intervening acts; and

scope of liability.

Thus:

Factual causation establishes a causal connection.

Legal causation determines the legal significance of that connection.

8. Remoteness of Damage

The law does not ordinarily impose liability for consequences that are too remote.

The leading common-law approach is based on reasonable foreseeability.

The basic question is:

Was the type of harm reasonably foreseeable as a consequence of the defendant's conduct?

If the harm is too remote, liability may be denied even though factual causation exists.

9. The Wagon Mound Principle

The famous Overseas Tankship (UK) Ltd v Morts Dock & Engineering Co Ltd (The Wagon Mound (No. 1)) decision established the modern foreseeability approach to remoteness in negligence.

Principle

A defendant is generally liable for damage of a kind that was reasonably foreseeable, rather than for every consequence that can be traced factually to the defendant's conduct.

Example

If oil is negligently discharged into a harbour and causes foreseeable pollution damage, that damage may be recoverable.

But if an extraordinarily unusual chain of events produces an entirely unforeseeable type of harm, the law may treat that harm as too remote.

10. Difference Between Factual and Legal Causation

11. Concurrent Causes

Sometimes more than one factor causes the injury.

For example:

A negligently injures B;

B is already suffering from a serious medical condition;

both factors contribute to the final harm.

The court may need to determine:

whether A's conduct materially contributed to the harm;

whether the injury would have occurred anyway;

whether multiple causes operate simultaneously.

Causation becomes particularly complex when there is no single exclusive cause.

12. Material Contribution

In some cases, the ordinary but-for analysis may be inadequate because several factors contribute to the harm.

The concept of material contribution may become relevant.

The basic idea is that where a defendant's breach materially contributes to the claimant's injury, causation may be established even though the defendant's conduct is not the sole cause.

This is particularly important in:

industrial disease;

medical negligence;

environmental injury;

occupational exposure.

13. Multiple Tortfeasors

Two or more defendants may independently contribute to the same injury.

Example:

Driver A negligently crashes into B.

Driver C then negligently causes a second collision.

B suffers serious combined injuries.

The court may have to determine:

what each defendant caused;

whether the harm is divisible;

whether liability is joint or several;

contribution between defendants.

14. Intervening Acts — Novus Actus Interveniens

An intervening act is a new event occurring after the defendant's conduct.

The Latin expression is:

novus actus interveniens

It refers to a new intervening cause that may break the chain of causation.

Examples include:

an independent third party's act;

extraordinary medical treatment;

deliberate criminal conduct;

highly abnormal natural events.

If the intervening event is sufficiently independent and unforeseeable, the original defendant may escape liability for later consequences.

15. Intervening Human Acts

Suppose A negligently leaves a loaded firearm unsecured.

B takes it and intentionally shoots C.

The court must determine whether B's intentional act constitutes an intervening cause breaking the chain between A's negligence and C's injury.

The answer depends upon factors such as:

foreseeability;

nature of the defendant's original risk;

independence of the intervening act;

whether the intervening act was itself a response to the original danger.

16. Medical Treatment as an Intervening Cause

Medical treatment does not automatically break the chain of causation.

If the claimant requires treatment because of the defendant's wrongdoing, ordinary medical complications may remain within the causal chain.

But exceptionally:

Grossly abnormal medical treatment may potentially become an intervening cause.

The question is whether the later treatment was sufficiently independent and unforeseeable.

17. Claimant's Own Conduct

The claimant's conduct may affect causation.

This can arise through:

contributory negligence;

failure to mitigate;

unreasonable conduct after the original injury.

For example:

A driver negligently injures B's leg. B then unreasonably refuses necessary medical treatment and suffers additional complications.

The court may have to separate:

harm caused by A; and

additional harm attributable to B's own unreasonable conduct.

18. Eggshell Skull Rule

A particularly important causation principle is the eggshell skull rule, sometimes called the thin-skull rule.

The principle is:

A defendant must generally take the claimant as found.

Suppose a defendant negligently causes a minor physical impact.

The claimant has an unusually fragile medical condition, and the injury becomes extremely serious.

The defendant may still be liable for the resulting extent of harm, even though the severity was unusual.

The defendant generally cannot argue:

"An ordinary person would have suffered only minor injury."

19. Case Law: Smith v Leech Brain & Co Ltd

This is a leading authority for the eggshell skull principle.

Facts

The claimant suffered a burn caused by the defendant's negligence. The injury triggered a pre-existing vulnerability that ultimately resulted in fatal consequences.

Principle

Once the defendant's conduct causes an actionable injury, the defendant may be responsible for the full consequences even if the claimant's particular vulnerability makes the consequences unusually serious.

Significance

The case distinguishes:

foreseeability of the type of injury

from

foreseeability of the precise extent of injury.

20. Causation and Foreseeability

Foreseeability generally does not require the defendant to predict the exact sequence of events.

The law commonly asks whether the general type or kind of harm was reasonably foreseeable.

Thus:

The precise manner in which an injury occurs need not always be foreseeable.

What matters is whether the resulting type of harm falls within the scope of foreseeable risk.

21. Case Law: Overseas Tankship (UK) Ltd v Morts Dock & Engineering Co Ltd

The Wagon Mound (No. 1)

This case established a major principle of legal causation.

Facts

Oil was negligently discharged into Sydney Harbour. The oil eventually ignited and caused fire damage.

Issue

Was the fire damage too remote?

Principle

The House of Lords held that recoverability depended on reasonable foreseeability of the type of damage.

Importance

The case established the modern foreseeability test for remoteness in negligence.

22. Case Law: Re Polemis

Re Polemis and Furness, Withy & Co Ltd

This earlier case adopted a broader approach to remoteness.

Principle

Once some damage was a direct consequence of the defendant's wrongful act, liability could extend to unexpected consequences.

The later Wagon Mound approach moved the law toward reasonable foreseeability.

Importance

Together, the two cases illustrate the historical development of legal causation:

Direct consequence → Reasonably foreseeable consequence.

23. Case Law: Barnett v Chelsea & Kensington Hospital

This is a leading authority on factual causation.

Facts

A man attended hospital after becoming ill. The doctor negligently failed to examine him properly.

He later died from arsenic poisoning.

Principle

The court concluded that even with proper treatment, the patient would have died.

Therefore, although there may have been negligence, the negligence did not factually cause the death.

Significance

The case clearly demonstrates:

Negligence without causation does not ordinarily establish liability for the particular damage claimed.

24. Case Law: Bonnington Castings Ltd v Wardlaw

This is an important authority concerning material contribution.

Facts

The claimant developed pneumoconiosis after exposure to dust at work.

Some of the dust exposure resulted from circumstances for which the employer was responsible.

Principle

Where the defendant's breach materially contributed to the disease, causation could be established.

Importance

The case demonstrates that causation does not always require proof that the defendant's conduct was the exclusive cause.

A material contribution can be sufficient in appropriate circumstances.

25. Case Law: McGhee v National Coal Board

This case is important in the development of causation principles involving occupational disease.

Principle

The claimant developed dermatitis after exposure to harmful materials during employment.

The precise scientific mechanism of the disease was uncertain.

The House of Lords treated the employer's failure to take precautions as materially increasing the risk of injury and accepted causation on the particular facts.

Significance

The case illustrates the difficulty of applying ordinary causal reasoning where scientific evidence cannot establish precisely which exposure caused the injury.

26. Case Law: Fairchild v Glenhaven Funeral Services Ltd

This is a major authority concerning exceptional causation problems in industrial disease.

Problem

Workers had been exposed to asbestos by multiple employers.

It was impossible to establish scientifically which particular exposure caused the disease.

Principle

The House of Lords developed an exceptional approach allowing liability where the defendant's conduct materially increased the risk of the relevant disease.

Significance

The case shows that courts sometimes develop specialized causal rules where ordinary "but-for" proof would make legitimate claims practically impossible.

27. Indian Case Law: Municipal Corporation of Delhi v Subhagwanti

Supreme Court of India

This case is important in the context of negligence involving a dangerous structure.

Principle

The Supreme Court applied principles associated with res ipsa loquitur in circumstances involving collapse of a structure.

The case demonstrates that where the nature of an event strongly indicates negligence, evidentiary principles can assist the claimant in establishing the necessary causal connection.

Importance

It illustrates the interaction between:

negligence;

causation;

evidentiary presumptions.

28. Indian Case Law: M.P. Electricity Board v Shail Kumari

Supreme Court of India

This is an important Indian authority concerning liability arising from dangerous electrical infrastructure.

Principle

The Supreme Court emphasized the responsibility associated with hazardous activities and the consequences of defective electrical systems.

Causation significance

Where dangerous infrastructure causes injury, courts examine the relationship between:

the hazardous condition;

the defendant's responsibility;

the accident;

and the resulting injury.

The case demonstrates the importance of causal responsibility in determining compensation.

29. Indian Case Law: Jacob Mathew v State of Punjab

Supreme Court of India

This case principally concerns medical negligence.

Principle

The Supreme Court emphasized that professional negligence requires careful evaluation of the applicable standard of care.

Causation significance

In medical negligence, it is not sufficient to show that the treatment was unsuccessful.

The claimant must establish an appropriate connection between:

breach of professional duty; and

resulting injury.

Thus:

Bad medical outcome ≠ automatically negligent causation.

30. Indian Case Law: Kusum Sharma v Batra Hospital & Medical Research Centre

Supreme Court of India

The Court discussed principles governing medical negligence.

Importance for causation

Medical negligence cases require consideration of:

professional standards;

medical evidence;

causal connection;

whether the alleged breach actually produced the injury.

The case illustrates why courts should avoid judging medical treatment solely from hindsight.

31. Cause-in-Fact Versus Cause-in-Law

Consider the following example:

A driver negligently drives at excessive speed.

B is injured.

C, a doctor, later treats B.

A factual chain may be:

A's speeding → collision → B's injury → medical treatment → complication

The court must determine:

Factual causation

Did A's driving cause B's initial injury?

Legal causation

Should A also be legally responsible for the later complication?

This requires examination of:

foreseeability;

intervening medical conduct;

claimant vulnerability;

mitigation.

32. Intervening Natural Events

Natural events can also affect causation.

Suppose:

A negligently leaves a building structurally unsafe.

Before it collapses, an extraordinary earthquake occurs.

The earthquake may potentially affect whether the defendant remains legally responsible.

The relevant question is whether the natural event was:

foreseeable;

independent;

extraordinary;

sufficient to supersede the original risk.

33. Intervening Criminal Acts

Criminal acts can create difficult causal questions.

Suppose:

A negligently creates a dangerous situation, and B subsequently commits an intentional crime exploiting that situation.

The court must determine whether B's criminal act:

was foreseeable;

was independent;

constituted a new intervening cause.

An intentional act does not automatically break causation.

34. Multiple Causes and Apportionment

Sometimes multiple causes contribute to harm.

For example:

40% attributable to defendant A;

35% attributable to defendant B;

25% attributable to claimant's own conduct.

The law concerning apportionment depends on the type of claim and jurisdiction.

In negligence, contributory negligence may reduce damages.

Where multiple tortfeasors are involved, principles of joint and several liability and contribution may apply.

35. Causation in Contract Law

Causation also matters in contract.

Under Section 73 of the Indian Contract Act, 1872, compensation is directed toward loss or damage that:

naturally arose in the usual course from the breach; or

was within the contemplation of the parties when they made the contract.

Thus contract law combines causation with remoteness.

For example:

A carrier fails to deliver machinery on time, causing a factory to stop operating.

The claimant must establish:

breach;

causal connection;

recoverable loss;

remoteness;

mitigation.

36. Hadley v Baxendale

This is the classic authority on contractual remoteness.

Principle

Damages are generally recoverable for:

losses arising naturally in the ordinary course of things; or

losses that were reasonably within the contemplation of the parties because of special circumstances communicated at the time of contracting.

Importance

The case demonstrates that causation and remoteness in contract are closely connected.

A breach does not automatically make the defendant liable for every financial consequence.

37. Causation in Criminal Law

Causation is also essential in criminal offences involving consequences such as:

death;

bodily injury;

property destruction.

For example, to establish criminal responsibility for causing death, prosecution may need to prove a causal connection between the accused's conduct and death.

The prosecution generally must establish:

Conduct → causal connection → prohibited consequence

beyond the required criminal standard of proof.

38. Factual Causation in Criminal Law

The but-for test can be useful:

Would the prohibited result have occurred without the accused's conduct?

However, criminal causation can involve additional considerations.

The accused's conduct need not necessarily be the only cause.

It may be sufficient that it was a legally significant cause, depending on the offence.

39. Legal Causation in Criminal Law

Criminal liability may depend upon whether the accused's conduct remained an operating and substantial cause of the result.

An intervening event may break the chain where it is:

independent;

extraordinary;

unforeseeable;

sufficiently powerful to make the original conduct no longer legally significant.

40. Causation and the "Thin Skull" Principle

The thin-skull rule demonstrates an important distinction.

Foreseeability asks:

Was the type of injury foreseeable?

Thin-skull principle asks:

Once injury is caused, must the defendant accept the claimant's unusual vulnerability?

Generally:

Yes.

Therefore, an unforeseeably severe consequence of a foreseeable injury may remain recoverable.

41. Causation and Mitigation

Mitigation is different from causation.

Causation

Asks:

Did the defendant cause the loss?

Mitigation

Asks:

Did the claimant take reasonable steps to prevent additional loss?

A defendant may therefore have caused the original injury while the claimant's later conduct reduces the amount recoverable.

42. Causation and Remoteness

These concepts should not be confused.

Causation

Determines whether the defendant's conduct produced the harm.

Remoteness

Determines whether the law considers the harm sufficiently connected to justify liability.

Thus:

Every legally recoverable consequence must have a causal connection, but not every factual consequence is legally recoverable.

43. Causation in Medical Negligence

Medical causation often requires expert evidence.

Courts may ask:

What treatment should have been provided?

What would probably have happened with proper treatment?

Did the breach materially worsen the outcome?

Was the patient's condition already terminal?

Did another medical condition cause the injury?

The claimant generally cannot establish causation merely by showing:

"The patient became worse after the treatment."

Temporal sequence is not necessarily causation.

44. Causation in Environmental Claims

Environmental litigation can involve:

pollution;

toxic exposure;

groundwater contamination;

industrial emissions;

ecological damage.

Causation can be particularly difficult because multiple sources may contribute.

Scientific evidence may be necessary to establish:

source;

exposure;

concentration;

pathway;

biological effect.

45. Causation in Product Liability

A defective product claim generally requires a connection between:

defect → use/exposure → injury

For example:

A defective pressure vessel explodes and injures a worker.

The claimant may need to establish:

defect;

causation;

injury;

applicable product-liability basis.

46. Causation in Professional Negligence

Professionals such as:

doctors;

lawyers;

accountants;

architects;

engineers

may face claims where their breach allegedly caused loss.

The claimant must generally establish not merely that professional conduct fell below the required standard but also that the breach caused the claimed loss.

47. Burden of Proof

The burden of establishing causation ordinarily rests upon the party asserting the claim, subject to specific statutory rules and evidentiary doctrines.

In civil cases, causation is ordinarily established on the:

balance of probabilities.

In criminal cases, causation must be established consistently with the:

beyond reasonable doubt

standard applicable to the prosecution's case.

48. Evidence Relevant to Causation

Courts may consider:

eyewitness evidence;

expert testimony;

medical records;

scientific evidence;

accident reconstruction;

photographs;

CCTV;

documentary evidence;

digital records;

statistical evidence;

chronology of events.

A well-constructed causal timeline can be extremely useful.

Example:

10:00 AM — Defendant's negligent act

↓

10:15 AM — Accident

↓

10:30 AM — Injury diagnosed

↓

2:00 PM — Medical treatment

↓

Next day — Complication

↓

One week later — Additional injury

The court can then examine which events are legally attributable to the defendant.

49. Common Causation Errors

Error 1 — Assuming sequence equals causation

Event B occurring after Event A does not automatically mean A caused B.

Error 2 — Ignoring alternative causes

A claimant may have suffered the same injury from an independent cause.

Error 3 — Treating negligence as sufficient

Negligence without causal damage does not automatically produce liability for damages.

Error 4 — Ignoring intervening events

Later events may break or alter the causal chain.

Error 5 — Confusing causation with remoteness

An event may be factually caused by the defendant but legally too remote.

50. Six Core Case Laws at a Glance

51. Step-by-Step Causation Analysis

When analyzing a legal problem involving causation, use the following sequence.

Step 1 — Identify the alleged wrongful act

What exactly did the defendant do or fail to do?

Step 2 — Identify the injury

What legally recognizable harm did the claimant suffer?

Step 3 — Apply factual causation

Ask:

Would the harm have occurred but for the defendant's conduct?

Step 4 — Identify alternative causes

Was another person, event, disease or natural force responsible?

Step 5 — Examine intervening events

Did a later event break the causal chain?

Step 6 — Apply legal causation

Was the harm within the legally recognized scope of the defendant's responsibility?

Step 7 — Consider remoteness

Was the type of damage reasonably foreseeable?

Step 8 — Consider claimant vulnerability

Does the eggshell principle apply?

Step 9 — Consider contributory negligence

Did the claimant's own conduct contribute to the damage?

Step 10 — Calculate recoverable loss

What portion of the harm is legally attributable to the defendant?

52. Overall Legal Test

A comprehensive causation analysis can therefore be expressed as:

Wrongful Conduct

↓

Factual Causation

"Did the conduct actually contribute to the harm?"

↓

Intervening Causes

"Did another event break the causal chain?"

↓

Legal Causation

"Is the connection legally sufficient?"

↓

Remoteness / Foreseeability

"Is the type of harm sufficiently connected and foreseeable?"

↓

Extent of Liability

"What loss should the defendant legally bear?"

53. Conclusion

Causation is the bridge between wrongdoing and legal liability. It prevents courts from imposing responsibility merely because a defendant behaved improperly and requires a legally sufficient connection between the defendant's conduct and the claimant's harm.

The two fundamental stages are:

Factual causation

Did the defendant's conduct actually cause or materially contribute to the harm?

Legal causation

Is that connection sufficiently close that the law should impose liability for the particular consequence?

The major authorities demonstrate different aspects of this doctrine. Barnett v Chelsea & Kensington Hospital illustrates the but-for test; Wagon Mound establishes reasonable foreseeability as a central principle of remoteness; Smith v Leech Brain establishes the thin-skull rule; Bonnington Castings and McGhee demonstrate material contribution in difficult scientific cases; Fairchild illustrates exceptional causation rules for industrial disease; and Hadley v Baxendale demonstrates the importance of causation and remoteness in contract.

Indian decisions such as Jacob Mathew v State of Punjab, Kusum Sharma v Batra Hospital & Medical Research Centre, M.P. Electricity Board v Shail Kumari, and Municipal Corporation of Delhi v Subhagwanti further demonstrate that causation operates across negligence, medical liability, hazardous activities and public-law compensation.

Ultimately:

Factual causation establishes that the defendant's conduct contributed to the harm; legal causation determines whether that contribution is sufficiently close, foreseeable and legally attributable to justify liability.