The recent decision in Dormer v Wilson and others [2025] EWHC 523 (KB) is the latest judicial application, in road traffic cases, of what now seems to be known as the illegality defence, having previously been widely referred to as the ex turpi causa rule. At its core is the relatively uncontroversial proposition that a civil claim arising from the claimant’s own wrongful act should be barred so as to ensure the integrity of the legal system between the criminal and civil fields.

In recent years, the Supreme Court has had to consider the basis and extent of the defence on several occasions and in very different factual settings. We will not rehearse that case law in this article but instead focus on how the defence was applied in Dormer.

Background

The facts were that the clamant and a relative, both teenagers without driving licences, were riding a stolen motorcycle when it collided with another vehicle at a junction in Birmingham city centre. Neither was wearing a helmet. The rider’s negligence was the sole cause of the accident, but there was some dispute as to which of them was at the handlebars. However, the judge found that evidence at the time of the accident given by police, ambulance staff and lay witnesses established that the claimant was the passenger on the bike.

As a passenger, three wrongful acts might have been laid at the claimant in order to establish the illegality defence. If any of them stuck, the defence would bite and bar his claim: its force is that it is a complete defence and not a partial one. The potential wrongful acts were: (i) allowing himself to be carried in a vehicle known to be stolen or unlawfully taken (s12 Theft Act 1968), (ii) dangerous driving (s2 Road Traffic Act 1988), and (iii) causing or permitting a vehicle to be used without insurance (s143 RTA).

Examination of witness evidence

After careful examination of the witness evidence – that of the claimant in particular – the judge held that none of these had been established.

First, he found on the evidence that the claimant did not know or suspect the motorbike had been stolen. The related questions of whether he knew or had reason to suspect it was not insured and what effect that might have on the liability of the insurer or that of the Motor Insurer’s Bureau were also examined but are not addressed in this article.

Second, the facts as found did not amount to a joint enterprise of dangerous driving, unlike the decision in McCracken v Smith, MIB and Bell 2015] EWCA Civ 380, which also involved two teenagers on a motorcycle colliding with another vehicle.

As regards the third potential offence, although the journey in which the claimant was injured was to some degree at his instigation because he wanted to be taken to hospital for medical treatment, he had nevertheless not “ 'caused' the defendant to 'use' the motorbike without insurance contrary to s.143(1)(b) RTA by… requiring to be taken to hospital on [it]”.

Contributory negligence

In Wallett v Vickers [2018] EWHC 3088 (QB) Males J observed that “careless driving is a criminal offence but nobody would suggest that careless driving by the claimant prevents the recovery of damages (reduced as appropriate on account of contributory negligence)”. In the present case, and by analogy, the judge adopted Males J’s reasoning to the causing use without insurance offence, stating that:

“[the] recovery of damages when a subsequently-injured passenger has (even knowingly) caused a driver to drive without insurance contrary to s.143 RTA is not harmful to the integrity of the legal system in the same way as dangerous driving. Again, a claimant is not compensated for the consequence of his own criminal act in encouraging driving without insurance, but for the consequences of the driver's negligence in injuring him and his foolishness can (and here in my view, does) sound in contributory negligence.”

This conclusion would seem to be entirely obiter, given that the judge did not find that the claimant had caused the s143(1) offence.

For all these reasons, the illegality defence failed. But, as suggested immediately above, the issue of contributory negligence was highly relevant. Reviewing the well-known authorities, the judge noted that in McCraken (above), failure to wear a helmet was one of several elements of contributory negligence – assessed in the aggregate at 65% by the Court of Appeal – that had been “agreed at 15% because it would have reduced injuries”.

The judge said he would have adopted this level if failure to wear a helmet was the only contributory feature. It was not, and a modest increase to 20% was appropriate on the facts. The claimant and defendant “may not have had a joint enterprise of joyriding, but they had a joint enterprise of bad-decision-making… [however] bearing in mind the claimant's young age and inexperience, his trust in the older first defendant who is clearly mainly responsible for the injuries and this being a case of poor decision-making by the claimant rather than reckless 'fun', the appropriate overall reduction (including for the absence of a helmet) is 20%.”

Future developments 

It is suggested that the outcome in Dormer does not amount to a further circumscription of the illegality (formerly ex turpi) defence, but instead an appropriate disapplication of it in light of the lack of criminality or turpitude on the claimant’s part. This recognises that the defence is grounded in protecting the integrity of the law by barring recovery if the harm arises out of the claimant’s wrongful act, not his or her merely foolish act. The truly new element in Dormer may prove to be the obiter analysis that even had the s143 offence been made out, it would not have triggered the illegality defence.  

There may be yet further development of the defence. The judge in Dormer noted that “the Supreme Court's work on illegality is not yet done: they granted permission to appeal Lewis-Ranwell v G4S & others [2024] EWCA Civ 138 where the Court of Appeal in yet another 'mental health unlawful killing' case held the illegality defence does not apply where the individual is unaware of their own criminality.”

The facts of that case read like an exam question. After the claimant had been negligently discharged from mental health care, he killed three elderly men in their own homes. He was charged with murder but was found not guilty by reason of insanity. He brought civil claims for the failure to provide adequate treatment and care.

In February 2024, the Court of Appeal held “by a majority of 2 to 1, that a person who deliberately and unlawfully kills whilst insane is not barred by the defence of illegality from suing mental health services for allegedly failing to treat him properly[1].” In May 2024, the Supreme Court granted the defendants’ request for permission to appeal, although a hearing date has yet to be listed. It has been described as “a truly shocking case on the facts [raising] ethical as well as legal issues and the Court of Appeal’s decision is likely to divide opinion sharply. However, there is currently no ruling on this precise situation from the highest court in the land[2]”.

[1] This passage is taken from a summary by Deka Chambers: Judgment handed down in Lewis-Ranwell v G4S Health Services & Others (2024) - Deka Chambers - Barristers Chambers

[2] In a case note published by NHS Resolution: Case of note: Lewis-Ranwell v. G4S Health Services (UK) Ltd., Devon Partnership NHS Trust and Devon County Council (Court of Appeal 16 February 2024) - NHS Resolution