DPP v Nock

DPP v Nock [1978] AC 979 is a decision of the House of Lords concerning the law of criminal conspiracy and the doctrine of impossibility. The case arose from the prosecution of Nock and a co-accused who had entered into an agreement to produce cocaine from a powder substance in their possession. The defendants believed, and had every subjective intention of acting upon that belief, that the powder contained cocaine in sufficient quantities to permit its extraction and purification into a usable controlled drug.

Expert scientific evidence adduced at trial established that the powder did not in fact contain cocaine. More significantly, the evidence demonstrated that no known chemical or scientific process could yield cocaine from that particular substance. The impossibility was therefore not merely a matter of practical difficulty or transient circumstance but was absolute and inherent in the nature of the materials themselves.

The defendants were nonetheless convicted at first instance of conspiracy to produce a controlled drug contrary to the relevant provisions of the Misuse of Drugs Act 1971. The prosecution's case rested on the proposition that the subjective agreement and intention of the defendants was sufficient to ground the conspiracy charge, regardless of whether the agreed objective was objectively achievable. The conviction was upheld on appeal before the matter was certified for consideration by the House of Lords.

The case therefore presented the House of Lords with a question of fundamental importance to inchoate criminal liability: whether the law of conspiracy at common law and under the Criminal Law Act 1977, as it then stood, extended to agreements whose subject matter was, as a matter of objective scientific fact, incapable of being carried out. The position of the defendants was that no true criminal conspiracy could exist in such circumstances, while the Crown contended that mens rea and agreement alone were sufficient.

The case fell to be decided against the backdrop of an unsettled and somewhat incoherent body of authority on impossibility in inchoate offences. The House had relatively recently addressed related questions in the context of handling stolen goods in Haughton v Smith [1975] AC 476, and the relationship between that authority and the law of conspiracy required careful analysis. The prevailing statutory framework was also in transition, the Criminal Law Act 1977 having recently codified aspects of conspiracy law, though the impossibility question was not expressly resolved by that legislation.

The central issue before the House of Lords was whether defendants could lawfully be convicted of conspiracy to produce a controlled drug in circumstances where it was scientifically impossible, by any known method, to produce that drug from the materials available to them. The question required the court to determine whether objective impossibility negated the actus reus of conspiracy or whether the mental element — the agreement and shared purpose — was alone sufficient to sustain criminal liability.

A subsidiary but related issue concerned the proper interpretation and scope of the Criminal Law Act 1977 in relation to impossible conspiracies, and whether the legislature, in codifying the law of conspiracy, had impliedly resolved the impossibility question in favour of liability or had left the pre-existing common law principles intact. The House was also required to consider how the principles articulated in Haughton v Smith [1975] AC 476 applied to the law of conspiracy specifically, rather than to the completed or attempted handling of goods.

Underlying both issues was the broader question of principle: what does criminal conspiracy protect against, and is the mischief targeted by conspiracy law the bare agreement between parties or the prospective harm that the agreed conduct would, if executed, bring about? The resolution of this question had direct implications not only for the parties but for the coherence of the law of inchoate offences more generally.

The House of Lords began its analysis by examining the conceptual foundations of the offence of conspiracy. A conspiracy at common law, and as codified in the Criminal Law Act 1977, requires an agreement between two or more persons to pursue a course of conduct which will necessarily amount to or involve the commission of a criminal offence. The crime of conspiracy is therefore not simply an agreement in the abstract but an agreement directed towards the commission of an actual, legally cognisable offence. The agreement must have, as its object, something that the law recognises as a crime.

Their Lordships reasoned that where the agreed objective is one which, as a matter of objective fact and not merely due to some contingent obstacle, cannot be achieved, the agreement cannot properly be characterised as an agreement to commit a crime. There is no crime to be committed. The parties may believe they are engaged in a criminal enterprise, but the criminal law does not attach liability on the basis of mistaken belief alone where the substantive offence is not merely difficult but impossible of commission in the relevant circumstances.

The House drew heavily on the reasoning in Haughton v Smith [1975] AC 476, in which the House had held that a defendant could not be convicted of attempting to handle stolen goods where the goods in question had, unbeknown to the defendant, ceased to be stolen goods by the time of his handling of them. The principle applied in that case — that impossibility negated liability for an inchoate or incomplete offence — was held to apply with equal if not greater force to conspiracy. If a defendant could not be convicted of attempt in impossible circumstances, it would be anomalous and logically inconsistent to convict him of the yet more inchoate offence of conspiracy to achieve the same impossible end.

The Lords were careful to distinguish between different categories of impossibility. Physical or inherent impossibility — of which the present case was an example — was to be distinguished from what might be termed relative or circumstantial impossibility, where the agreed crime could in principle be committed but circumstances on a particular occasion rendered it impracticable. The law of conspiracy was not intended to penalise parties simply because they laboured under a factual error about the material properties of the substance with which they were dealing, where that error meant that no crime was or could be committed.

The distinction between inherent impossibility and mere difficulty or contingent failure was central to the ratio. The court recognised that conspiracies may be frustrated, incomplete, or ultimately unsuccessful without this affecting the validity of the conspiracy charge. However, where the very agreement itself relates to an act that can never constitute a crime because it is physically impossible, the agreement lacks the necessary quality of being directed at criminal conduct. The defendants in the present case could not produce cocaine not because they lacked the means or opportunity in a contingent sense, but because the material they had was incapable of yielding cocaine by any means whatsoever.

The House considered the argument advanced by the prosecution that the defendant's subjective belief — their genuine conviction that the powder contained cocaine — was sufficient to supply the mental element for conspiracy and that the law should therefore impose liability. Their Lordships rejected this contention. The mental element in conspiracy is, of course, a necessary ingredient of the offence, but it is not sufficient in isolation. The agreement must still be directed towards a course of conduct that is objectively criminal. Subjective criminality, untethered from any objective criminal act or course of conduct, does not suffice to ground inchoate liability in English law as it then stood.

The House also addressed R v Doot [1973] AC 807, which had affirmed the vitality and importance of the law of conspiracy as a means of addressing criminal enterprises at an early stage. In Doot, the conspiracy had been entered into abroad but partly executed in England, and the question was one of jurisdiction rather than impossibility. The House distinguished Doot on the basis that the agreement in that case was directed at genuinely criminal conduct — the importation of controlled drugs — which was entirely possible of achievement. Doot therefore provided no authority for the proposition that an agreement to do the impossible could constitute a conspiracy. The principles affirmed in Doot as to the nature of conspiracy as an agreement directed at criminal ends in fact supported rather than undermined the conclusion in the present case.

Their Lordships also turned to the Criminal Law Act 1977, which had recently introduced a statutory framework for conspiracy, in part as a response to judicial concerns about the overextension of the common law offence. The 1977 Act defined conspiracy in terms of an agreement to pursue a course of conduct which, if the agreement were carried out in accordance with the parties' intentions, would necessarily amount to or involve the commission of any offence. The House held that this formulation, properly construed, did not extend to agreements to do the objectively impossible. The phrase "would necessarily amount to or involve the commission of any offence" presupposed that the agreed conduct was capable of amounting to a criminal offence — a condition not satisfied where the conduct was inherently impossible of achievement.

Lord Scarman, in an influential speech, acknowledged the practical difficulties and the unsatisfactory state of the law as it emerged from the decision in Haughton v Smith [1975] AC 476 and the present case. His Lordship observed in terms that the law governing impossible attempts and conspiracies was in need of legislative clarification and reform. The existing position produced results that were capable of appearing anomalous — particularly the contrast between a defendant who attempts or conspires to do something possible but fortuitously fails, and one who genuinely and wholeheartedly believes they are engaged in criminal conduct but whose enterprise is objectively impossible. Lord Scarman's observations constituted an express invitation to Parliament to address the lacuna.

The court recognised that the outcome in the present case might be perceived as unsatisfying from a policy perspective, since the defendants were morally culpable and had the full intention to engage in serious criminal activity. However, their Lordships were firm that the existence of moral culpability and criminal intent is not, without more, sufficient to ground criminal liability in a system governed by the rule of law. The function of the court is to apply the law as it stands, not to extend liability beyond its proper boundaries in response to the perceived dangerousness or blameworthiness of the accused. The task of extending the law, if extension were warranted, lay with Parliament.

The House of Lords allowed the appeal and quashed the convictions of the defendants. It held that where a conspiracy charged against defendants relates to an object that is scientifically and objectively impossible of achievement — in this case the production of cocaine from a substance incapable of yielding that drug by any known process — no criminal conspiracy exists in law. The agreement, however sincerely made and however firm the defendants' shared intention, is not an agreement to commit a crime because the crime agreed upon cannot be committed.

The principle of impossibility as a defence to conspiracy was thus confirmed. The decision extended and applied the reasoning of Haughton v Smith [1975] AC 476 to the specific context of conspiracy, holding that objective impossibility defeats liability for the inchoate offence regardless of the subjective intentions and beliefs of the conspirators. The conspiracy requires an agreement directed at conduct that is, in objective terms, capable of constituting a criminal offence.

The House declined to extend criminal liability on the basis of the defendants' mistaken belief alone, holding that the law of conspiracy as it stood — both at common law and under the Criminal Law Act 1977 — did not criminalise agreements whose subject matter was inherently incapable of constituting a crime by reason of objective impossibility. The correct course was for Parliament, not the courts, to remedy any perceived shortcoming in the law.

DPP v Nock occupies a pivotal position in the development of inchoate offence law in England and Wales. The decision, together with Haughton v Smith [1975] AC 476, exposed what was widely perceived as a significant lacuna in the criminal law: the inability to convict individuals who harboured genuine criminal intent but whose plans were defeated by objective impossibility. The express call for legislative reform made by Lord Scarman was heeded by Parliament in the form of the Criminal Attempts Act 1981, section 1 of which specifically abolished the impossibility defence in the context of criminal attempts, providing that a person may be guilty of attempt even if the facts are such that commission of the offence is impossible.

The impact of the 1981 Act on the law of conspiracy is more nuanced. The Act addressed impossibility in the context of attempts directly, and the courts subsequently grappled with the extent to which the same policy reversal applied to conspiracy. The significance of this was demonstrated in R v Shivpuri [1987] AC 1, in which the House of Lords overruled its own earlier decision in Anderton v Ryan [1985] AC 560 and held that the 1981 Act meant that impossibility was no longer a defence to a charge of attempt. Nock itself was not overruled in respect of conspiracy, but the legislative momentum it helped generate profoundly reshaped the broader law of inchoate offences.

The case remains significant for the study of criminal law for several reasons. First, it illustrates the historic distinction between subjective and objective approaches to inchoate liability and demonstrates that English law, at the time of the decision, anchored conspiracy in objective rather than purely subjective criteria. Second, it provides a clear illustration of the relationship between judicial law-making and legislative reform: the House of Lords, recognising the limits of its proper constitutional role, declined to extend the law beyond established principle and instead invited parliamentary action. Third, Nock remains relevant to the law of statutory conspiracy under the Criminal Law Act 1977 to the extent that it confirms the interpretive approach to the Act's definition of conspiracy and its interplay with impossibility, an area where the law continues to reward careful analysis.