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Medical Negligence: When Negligence And Unforeseen Consequences Collide

Reasons to choose Wilson Browne

Can Medical Negligence Break the Chain of Causation?

Let’s start with putting that into plain English in simple terms: what that in effect means in this instance, is that an act of negligence causes an effect that was (and probably couldn’t have been) anticipated, leading to an outcome that was worse than anyone would reasonably have foreseen.

A non-medical negligence example might be that in a friendly ‘knock about’ of cricket, the nets around the pitch aren’t put up (negligence) and a ball is hit through someone’s kitchen window, smashing it (which could be foreseen). The ball (having smashed the window) drops into a chip pan causing the chip pan to spill over, ignite on the gas hob, set fire to the kitchen blinds…and burns the house down – which nobody could have anticipated.

Causation in medical negligence cases is important because it is about proving that negligence has occurred as a result of a breach in a duty of care.

To bring a claim of medical negligence, this breach must have caused injury to the claimant.

A break in the chain of causation in medical negligence can happen where an unforeseeable event that occurs after a neglectful act intervenes and worsens the effects of the injury on the claimant.

Where there is a break in the chain of causation, this may mean that the defendant will not be found liable, even if there is proof that they acted negligently.

Proving Causation in Medical Negligence

Proving causation in medical negligence claims can be difficult because it requires a clear chain of cause and effect. There can be cases where injury, damage or loss would have occurred even if there was no negligent action involved.

It can still be difficult to establish causation even when you apply the principle of material contribution. Material contribution is where there is proof that negligence made more than a minimal contribution to the injury the claimant suffered.

Proving clinical negligence causation relies on the balance of probabilities showing that a breach in duty of care was the reason for the claimant’s injury.

With many medical treatments and procedures, there is an acceptance that potential complications may affect the outcome. This is where the balance of probabilities can be crucial.

Things can become further complicated where there are multiple factors involved, which could also have contributed to the injury.

However, if these multiple factors are shown to be cumulative, then this may mean a claim can still succeed.

What is a Break in the Chain of Causation?

In legal language, breaking the chain of causation is known as novus actus interveniens.

The break occurs due to an unforeseen event occurring after a neglectful act, which worsens the effects.

To break the chain in this way, the claimant must act in such a way that this obliterates the original neglectful act of the defendant.

For example, if someone has a leg injury which is proved to be the result of medical negligence, but they continue to use the leg in situations that put them at risk, they may go on to injure themselves further. This would then break the chain of causation.

But can further actions of the defendant, rather than the claimant, in medical negligence cases, also break the chain of causation?

Does Medical Negligence Break the Chain of Causation?

One principle behind the chain of causation is that as long as the defendant’s conduct is an effective cause of the claimant’s injury, the chain is unlikely to break.

Therefore, if a defendant’s actions in a medical negligence case led to unforeseeable events causing further injury to a claimant, this would not break the chain of causation.

For more information about how our medical negligence team can help you, please contact us.

Louise Tyler


Louise Tyler


Louise is the Head of the Medical Negligence Team working in this area of law for 25 years. She is a member of the Law Society Clinical Negligence Panel, the AvMA (Action for Victims of Medical Accidents) Panel and been appointed to the Executive Committee…