Volenti Non Fit Injuria
Establishing the Defence
To establish the defence of volenti non fit injuria, the defendant must show that:
- The claimant had fully-informed knowledge about the risk; and
- The claimant voluntarily agreed to waive their right to sue if the risk manifested, or otherwise indicated that they assumed the risk themselves and so would not sue: Nettleship v Weston  2 QB 691.
Ordinarily, an express indication that the claimant is waiving their right to sue is needed. However, the courts will sometimes infer that the claimant has voluntarily assumed responsibility for their risk from their actions.
The claimant must be capable of appreciating any obvious risks and understanding what he is doing. This may not be the case if he is too drunk or incapacitated. It is not enough that the claimant is merely disinhibited, however: Morris v Murray  2 QB 6.
It does not matter that the claimant, having understood the risk, thought that it would nor happen to him: Imperial Chemical Industries Ltd v Shatwell  AC 656.
The courts are generally reluctant to imply a waiver, without express agreement, from the mere fact that the claimant engaged in a risky activity with knowledge of the risk: Smith v Baker  AC 325. However, the court may infer a waiver in cases based on the following factors:
If their employer ordered the claimant not to perform the action, whether serious measures were taken to enforce the order or the claimant was under pressure or encouragement from a superior to do the act: Imperial Chemical Industries Ltd v Shatwell  AC 656.
The claimant incited, co-operated or assisted the defendant in creating the risk (with knowledge that what he was doing was risky): Morris v Murray  2 QB 6.
There was no need (beyond the claimant’s entertainment) or compulsion for the claimant to do the risky act: Morris v Murray  2 QB 6.
The risk was serious and obvious: Morris v Murray  2 QB 6.
Possibly where there was no social or physical inconvenience in avoiding the situation, though this is a weak factor which must be supported by others: Dann v Hamilton  KB 509.
This will be a determination based on degree and the facts of the particular case.
When Does the Defence Not Apply?
The defence of volenti non fit injuria cannot be relied on where the purpose of the defendant’s duty was to protect the claimant from doing the relevant risky action: Kirkham v Chief Constable of Greater Manchester  2 QB 283.
Motor Vehicle Accidents
Volenti non fit injuria is unavailable where the claimant is the passenger in a motor vehicle accident: Road Traffic Act 1988, s 149(3).