Discuss causation in criminal law.
Generally, causation can be said to be a difficult area of law.  Causation could be proved either through factual or legal causation. According to the Court of Appeal in Pagett  and Cheshire  the issue of factual causation is mainly one for the jury once it has been determined by the courts that there is enough evidence to be left to them. Factual causation can be established through the ‘but for’ test 
When establishing legal causation, the accused need not be the sole or even the main cause of the harm or victim’s death but it must be a significant cause of the result 
In the case of R v Kennedy No2  , it was held that the defendant’s contribution need only be significant, it need not be substantial. In circumstances where there are no complicating factors, factual causation will be sufficient to establish causation but where there are complicating factors, legal causation will be needed to establish causation.
In Pagett, Goff LJ  asserted that ‘it is left for ‘the judge to direct… in simple terms, in accordance with the legal principles which they have to apply. It would then fall to the jury to decide the relevant factual issues which, identified with reference to those legal principles, will lead to the conclusion whether or not the prosecution have established the guilt of the accused of the crime of which he is charged’.
The chain of causation can be broken by a novus actus interveniens  . Simester and Sullivian explained in their book that a ‘novus actus’ is an action or an event which ‘intervenes’ to ‘break the causal chain’ leading from D to the eventual harm”. Where the result is attributable to a novus actus, D is relieved of the liability for that result and his conduct is no longer seen as a significant and operating cause. 
Not in all cases will an intervening act break the chain of causation. There are some situations where the defendant has to take his victim as he finds him. For example in the cases where the victim refused medical treatment based on religious beliefs  or pre existing medical, mental or physiological conditions as seen in the cases of Hayward,  Jordan,  smith  and Blaue.  Lawton L. J held that “it does not lie in the mouth of the assailant to say that the victim’s religious beliefs which prevented him from accepting certain types of treatment were unreasonable”  . So the refusal of your victim to treatment would not relieve you of liability in the thin skull rule. And so it wouldn’t break the chain of causation.
Where the defendant is still a significant and operating cause at the time of the victim’s death, then it is irrelevant that there are other causes too also operating and this was the view in Blaue, Smith and Dear (1996)  . Norrie was of the view that what might be apposite for breaking the chain of causation in such case which is necessary in order to distinguish the religious from the spiteful victim was not provided by the law commission. 
Honore and Hart argue that where there is a free, deliberate and informed act or omission of a human being intervening in causal sequence, the initial causal chain is broken. 
The issue of causation becomes confusing when it comes to drug administration and joint responsibility cases under novus actus intervenien. Different academic writers have also commented on this view. The case of Kennedy No2 was seen to be the leading case with regards to the causation principles in cases of supply drugs where the dealer supplies drug and after voluntary self injection by the victims, they die.
The approach to causation may be based on the specific unlawful act used at the trial, in R v Kennedy (No 2), R v Carey  and R v Dhaliwal  , there appears to be an exact incongruous application of causation all of which involved an unlawful act so less important in nature. 
Thirlaway and James were of the view that the decision in Kennedy No2 did not attract a great deal of the academic support. 
In Kennedy No2, the appellant was convicted of manslaughter and supplying a class A drug (heroin) which is contrary to s.4 (1) of the Misuse of Drugs Acts 1971.  He was sentenced to five and two years’ imprisonments on the first and second counts respectively to run simultaneously. The convictions arose out of the death of the Victim, B, who died as a result of 'inhalation of gastric contents while acutely intoxicated by opiates and alcohol' (at ). On 10 September 1996, the appellant visited the room occupied by the victim and his friend, C, who had been drinking together. According to the evidence of C, B told the appellant that he wanted ‘a bit to make him sleep'. The appellant had told the victim to take care that he did not go to sleep permanently. The appellant prepared a syringe of heroin and gave it to the victim. The victim injected himself and returned the empty syringe to the appellant, who then left the room. The victim then appeared to stop breathing and was pronounced dead when he was taken to hospital.
The appellant was given leave to appeal but his first and second appeals were dismissed. The appellant challenged it on the point of law and was therefore heard by the House of Lords and so his third appeal was allowed.
Thirlaway and James asserted that the Court of Appeal in Kennedy (No. 2) was suggesting that the appellant and the victim were joint principals as far as the s.23  offence was concerned and that therefore a causal link could be established, albeit tenuously. 
Having analyzed and found unquestionable the elements of the s. 23  and manslaughter offences, the House of Lords in Kennedy No2 went on to consider principles of causation in depth and agreed (at ) that the 'free, deliberate and informed intervention of a second person, who intends to exploit the situation created by the first, but is not acting in concert with him, is normally held to relieve the first actor of criminal responsibility 
Analyzing the previous case law briefly, the House of Lords were of the view that Cato  could be distinguished from Kennedy No1 on its facts as the Injection had been administered by the defendant.
The House of Lords concurred with the judgments in R v Dalby  and R v Dias  that the chain of causation could be broken by the voluntary and informed decision of the person injecting himself. As a result, it was held that the case of R v Rogers  had been wrongly decided. In Kennedy (No. 2), the Court of Appeal found that the jury could have validly convicted the appellant of manslaughter if they were satisfied that, when the syringe was handed to the victim for the purposes of 'immediate injection' (at ), the appellant and the victim were both engaged in the activity of administering the heroin.
The Court of Appeal found that there was no need for the jury to find the presence of encouragement and that the jury were entitled to find that the victim and the appellant were jointly engaged in administering the heroin. In finding this, it was inevitable that there was a joint unlawful act contrary to s. 23 which had, in fact and in law, caused the deceased's death. In applying this approach, the problem of what appeared to be a novus actus interveniens in the chain of causation was avoided. Ormerod and Forston describe the court's approach as a 'controversial ... unworkable approach to liability based on D's "joint participation", criticizing not only the interpretation of the words 'any other person' under s. 23 but also the reasoning behind the concepts of joint liability. 
Cowan  asserted that in prosecuting a manslaughter case, you must be able to prove that the defendant caused the death. A voluntary intervening act by a responsible person breaks the chain of causation. Williams asserted that what a person does is his own responsibility and is not regarded as having been caused by other people. This approach has been repeatedly adopted and approved by the appellate courts in a diverse range of circumstances like Pagett and Latif  . In the context of drug administration cases; the courts have released their grip on this seemingly settled principle.
Ormerod explained that after years of confusions in the Court of Appeal, the House of Lords were able to restore orthodoxy back to the principles of causations in a judgment delivered by Lord Bingham. Ormerod asserted that it was a most welcome conclusion and was obvious to all commentators. 
Lord Bingham clarified that the decision in Empress Car Co  is restricted to cases of pollution or environmental crimes: “it does not lay down any general rules governing causation in criminal law”
The Court of Appeal accepted that in Dias that the principal act of self-injection is not a crime and thus there can be no form of accessory liability for it. Williams, R asserted that the position in criminal law before Finlay  was simple in the sense that if the defendant had directly caused the offensive result, he would be guilty as a principle  40
Under the doctrine of joint enterprise, the principles of causations cannot be relied on due to a number of unfortunate reasons which was explained by Virgo G  42
Reed asserted that helping or encouraging another to commit an offence is a specific crime and D is liable in such a case as a secondary party but V is not liable because there is no offence of self manslaughter and he has committed no crime.  Hughes was of the view that only one person can inject the drugs, so how then can a drug be jointly administered? It would surely be impractical for two people to depress the plunger simultaneously. He said that Lord Bingham’s comments were obiter and should remain so because it is difficult to sustain term ‘jointly administered’ unless Lord Bingham was referring to cases such as Cato. 
Reed was of the view that ‘consistency and legal principle does not permit us to create an exception to the general principles of causation to take care of the particular problem thrown by the case’. 
The important case of Environment Agency v Empress Car Co. (Abertillery) Ltd fits uneasily with the general principle of voluntariness expressed in Latif. The decision in Empress is perhaps best explained in terms of public policy concerns over tile control of pollution but unfortunately their Lordships appeared to confuse culpability and specific interpretation of legislation, with causation. 
The outcome in Empress was that a deliberate intervening act does not break the chain of causation unless extraordinary. Following the general principle in Latif, the bandit’s act should have broken the chain of causation but it didn’t. The court of appeal held that The Court of Appeal in Dias asserted that, in cases where D is accused of manslaughter because he supplied V with drugs, a conviction can only be upheld if the issue of causation is left to the jury to decide  . This formed a mark of separation between Kennedy and Dias 
Cherkassy disagreed with the decision in Kennedy No2 on the fact that the act of injection was to break the chain in causation because the injection was made possible by the unlawful act of possession and supply of drugs and the victim administering the drug does not mean the defendant didn’t take part in the administration. 
There have been inconsistency and different confusing views as regards the principles of causation. There has not been a unanimous decision on the issue of causation. In R v Dias, the Court of Appeal asserted that the victim acting fully informed and deliberate would not break the chain of causation while in Kennedy No2, the house of lords ruled that D is not guilty of UAM in cases where V injects himself with the drug and was fully informed and responsible adult and therefore would break the chain of causation. This decision was welcomed by many academics.  Also the Court of Appeal in R v Evans  has now ruled that the supplier may instead be guilty of gross negligence manslaughter if he finds out that his victim has become seriously ill but does nothing to save him. In Cato, it was held that anyone who injects a person who consents with a controlled drug is guilty under s.23 of OAPA and thus of UAM if he later dies.
Rogers was of the view that the law needs clarification and amendment. 
In summary, I would concur with Reed on the issue of UAM that the laws relating to UAM is in total mess and has been approached in a confused manner and he asserted that “the recent decisions in Kennedy and Dias are palpably inconsistent over the issues of causation, voluntariness and assistance in drug-abuse injection. It is high time for the House of Lords to enter the vanguard to point us in the right direction. Confusion reigns supreme”.