Causation is the critical consideration in Hughes v R  UKSC 56 (31 July 2013). The offences under analysis, punishable by imprisonment for up to two years, are causing death while driving without a licence, and without insurance, contrary to s 3ZB of the Road Traffic Act 1988:
"A person is guilty of an offence under this section if he causes the death of another person by driving a motor vehicle on a road and, at the time when he is driving, the circumstances are such that he is committing an offence under-
- Section 87(1) of this Act (driving otherwise than in accordance with a licence); ...
- Section 143 of this Act (using a motor vehicle while uninsured or unsecured against third party risks)."
The agreed facts were that all fault lay with the victim, and there was nothing objectionable about the appellant's driving other than his lack of an appropriate licence and his lack of insurance. A collision occurred when the victim's car crossed the centre line on a bend and struck the appellant's vehicle, and the victim subsequently died from injuries sustained in this accident. The victim had been driving erratically for some time before the accident, had been using heroin, and was overtired. The appellant could not have avoided the collision, but he was charged with the two offences created by these paragraphs of this section.
At first instance the Recorder ruled that causation had to be proved, and the Crown successfully appealed that ruling. The Court of Appeal followed its decision, delivered after the Recorder's ruling, in R v Williams  EWCA Crim 2552;  1 WLR 588 in which it had held that the offences required simply that the defendant had no licence or insurance, that he was driving and had been involved in a fatal crash; there was no requirement of proof that the defendant had exhibited any fault contributing to the accident. The Supreme Court overturned this, holding:
" ... it must follow from the use of the expression "causes…death…by driving" that section 3ZB requires at least some act or omission in the control of the car, which involves some element of fault, whether amounting to careless/inconsiderate driving or not, and which contributes in some more than minimal way to the death. It is not necessary that such act or omission be the principal cause of the death. In which circumstances the offence under section 3ZB will then add to the other offences of causing death by driving must remain to be worked out as factual scenarios are presented to the courts. In the present case the agreed facts are that there was nothing which Mr Hughes did in the manner of his driving which contributed in any way to the death. It follows that the Recorder of Newcastle was correct to rule that he had not in law caused the death by his driving. The appeal should be allowed and that ruling restored."
In Williams the Court of Appeal had reasoned that when s 3ZB was created, so too was s 2B, which is an offence of causing death by careless driving, so the offences against s 3ZB must involve less than carelessness, and indeed as a matter of statutory construction they did not require an element of fault. An analogy was drawn with R v Marsh  1 Cr.App.R. 67, in which it was sufficient that the defendant's driving was a cause of the accident which was an element of the offence of aggravated vehicle taking, created by 12(A)(1) of the Theft Act 1968. The focus in Williams was therefore on whether the defendant's driving had been a cause of the accident.
But in Hughes the Supreme Court reasoned that although the appellant's driving could be seen as a "but for" cause of the victim's death, in the sense that it set the scene for the accident, that did not resolve the question whether the appellant's driving was a legally effective cause of the death -.
If Parliament had wanted to impose liability without causation, it could have done so by unambiguous language, however :
"...A penal statute falls to be construed with a degree of strictness in favour of the accused. It is undoubtedly open to Parliament to legislate to create a harsh offence or penalty, just as it is open to it to take away fundamental rights, but it is not to be assumed to have done so unless that interpretation of its statute is compelled, and compelled by the language of the statute itself. The rule of construction which applies to penal legislation, and a fortiori to legislation which carries the penalty of imprisonment, is not identical to, but is somewhat analogous to, the principle of statutory interpretation known as the principle of legality."
The Court referred  to Lord Hoffmann's remarks on legality in R v Secretary of State for the Home Department Ex p Simms and O'Brien  2 AC 115, 131E, to the effect that in the absence of clear and unambiguous language there was too great a risk that Parliament may have not appreciated the implications of what it was legislating.
"It follows that in order to give effect to the expression "causes…death…by driving" a defendant charged with the offence under section 3ZB must be shown to have done something other than simply putting his vehicle on the road so that it is there to be struck. It must be proved that there was something which he did or omitted to do by way of driving it which contributed in a more than minimal way to the death. The question therefore remains what can or cannot amount to such act or omission in the manner of driving."
Then, turning to what sort of driving might be sufficient to establish this causal connection, the Court at - declined to accept a suggestion, by Professors Sullivan and Simester in  Criminal Law Review 754, that responsibility may attach without culpability, as for example where the defendant in the agony of the moment swerved the wrong way, or where he encountered an unexpected natural hazard such as ice. The difficulties with those suggestions became clear if one asked why a driver should be responsible for the death of a person who caused him to swerve but not for the death of some third and in other respects uninvolved person, or why a natural hazard should have different consequences from a manmade hazard.
No indeed , to avoid confusion and incoherence in the law, the Court held that under this section a defendant
" ... is guilty of causing death only when there is some additional feature of his driving which is causative on a common sense view and the latter entails there being something in the manner of his driving which is open to proper criticism. To give effect to the words "causes…death…by driving" there must be something more than "but for" causation. ... The statutory expression cannot, we conclude, be given effect unless there is something properly to be criticised in the driving of the defendant, which contributed in some more than minimal way to the death."
This still does not require negligence, and as an example of something less than negligence but sufficient to establish the causal link required by s 3ZB, the Court suggested  a driver who slightly exceeded the speed limit and as a result could not avoid the accident, or a driver who failed to discover a fault in his vehicle that would have been readily apparent such as an underinflated tyre or a tyre with insufficient tread. However the Court stressed that it was unwise to attempt to foresee every possible scenario, and that it remained to be seen whether the offences against s 3ZB (including a third offence, provided for by paragraph (b), involving driving whilst disqualified ) added much to the offence of causing death by careless driving.
The statutory language in Marsh, above, was different but there was still an open question about causation in that context that was not necessary to decide in this appeal .
I have previously discussed responsibility in the context of dangerous driving: R v Roy, 2012 SCC 26, on 15 June 2012, where actus reus and mens rea were the analytical tools used for determining dangerousness. That focus is different from the issue in Hughes, which is the causal element of responsibility.