## Facts

- The defendant’s servant left a pair of horses unattended on a busy street.
- The horses became startled and bolted, creating a danger to people in the vicinity.
- A police constable intervened to stop the horses, aiming to protect others from harm.
- The constable sustained injuries during the rescue.
- The defendant argued the constable’s actions were voluntary and absolved them of liability.

## Issues

1. Whether the defendant owed a duty of care to a rescuer injured while preventing harm caused by the defendant’s negligence.
2. Whether the rescuer's voluntary intervention broke the chain of causation as a _novus actus interveniens_.
3. Whether the defense of _volenti non fit injuria_ applied, barring recovery due to voluntary assumption of risk.
4. Whether the principle established extends to situations where a rescuer's act is reckless or unreasonable.

## Decision

- The Court of Appeal held the defendant owed a duty of care to the claimant.
- It was found reasonably foreseeable that leaving horses unattended could lead to such a danger and intervention by third parties.
- The constable’s act of rescue did not amount to a _novus actus interveniens_; the chain of causation remained unbroken.
- The defense of _volenti non fit injuria_ did not apply, since the constable was acting under a general duty and not voluntarily assuming the risk in law.
- The defendant was held liable for the injuries sustained by the constable during the rescue.

## Legal Principles

- The “rescuer principle” is established: a defendant who creates a dangerous situation through negligence will be liable for foreseeable injuries to rescuers acting reasonably.
- Acts of rescue in response to imminent danger from a defendant’s negligence are not considered to break the chain of causation.
- The defense of _volenti non fit injuria_ is inapplicable where the rescuer acts out of duty or necessity, rather than free acceptance of risk.
- The court distinguishes between reasonable rescue attempts and reckless interventions that might fall outside the protection of this principle.
- Reasonable foreseeability is central in establishing the duty of care and scope of liability.

## Conclusion

The case affirms that defendants are liable for foreseeable injuries sustained by rescuers responding reasonably to dangers created by the defendants’ negligence, with the rescuer principle limiting both the application of the _volenti non fit injuria_ defense and the interruption of causation in such situations.


Haynes v Harwood [1935] 1 KB 146 (CA)