In previous posts we have considered the legal mechanisms for imposing criminal liability on secondary parties (aiding and abetting) as well as participants in a joint enterprise. Those two mechanisms have something in common: The people caught within their net may not have committed any physical, substantive crime. If D persuades P to stab V, D is guilty of abetting murder even though he has not physically killed anybody. Similarly, if D takes part in a joint criminal enterprise with P, and in the course of that enterprise P shoots V in the head, D may be guilty of murder notwithstanding the fact that D did not physically kill anybody.

Conspiracy shares this common feature. It imposes criminal liability on those who form an agreement to commit a crime, whether or not that crime actually takes place.

Conspiracy, along with criminal attempts, falls under the category of inchoate offences. According to the dictionary, inchoate means:

Not yet completed or fully developed; rudimentary.

Once one has formed an agreement to embark on a criminal endeavor, one has taken the first step towards a “fully developed” criminal offence. Since the offence has not yet been committed, the whole criminal endeavor is incomplete, or inchoate. Given a choice between a simple word and an ossified old word of Latin origin, the law always seems to plump for the latter. Maybe it has something to do with lawyers’ fees…

In the next few sections we will consider the legal rules and principles surrounding conspiracy. What is an “agreement”? What are the mens rea requirements? Can one conspire to commit an impossible act? We will also take some time to reflect on the rationale underlying this area of criminal law.

The Basics

Conspiracy is an aged member of the common law, developed by the judiciary over countless centuries. Its aim was, and is, to bring within the remit of criminal law those who form an agreement to commit a crime at some future date.

The law was placed on a statutory footing by the Criminal Law Act 1977, section 1(1):

Subject to the following provisions of this Part of this Act, if a person agrees with any other person or persons that a course of conduct shall be pursued which, if the agreement is carried out in accordance with their intentions, either—

(a)will necessarily amount to or involve the commission of any offence or offences by one or more of the parties to the agreement, or

(b)would do so but for the existence of facts which render the commission of the offence or any of the offences impossible,

he is guilty of conspiracy to commit the offence or offences in question.

The actus reus is clear: the offence is completed as soon as an agreement is reached with any other person or persons. So, if D and P form an agreement that P will rob the Bank of England next Tuesday, the offence of conspiracy to commit robbery is made out. If the police pick-up on the agreement – perhaps via covert surveillance or a prescient tip-off – they can arrest D and P and charge them with a criminal offence.

The mens rea of the offence also looks pretty clear: intention. This is explicitly stated under section 1(2) of the Act. But what must one intend? Will it be sufficient that D simply intended to form an agreement (that is, that D deliberately agreed to commit a criminal offence)? Or does D have to intend that the substantive offence will be committed? All will be explained below, where we consider mens rea in more depth.

Section 1(1) also makes it abundantly clear that one can form a conspiracy notwithstanding the fact that the offence to which one has agreed is actually impossible to commit. In the service of clarity, let us consider an example:

Rachel and Andrea are members of a gang known as the “Los Pollos Hermanos”. They earn their superabundant salaries by producing, distributing, and selling the drug known as “crystal meth”. Unfortunately for them, a particularly astute police officer suspects them of drug dealing. He installs a bug in their secret bunker and records their conversations. One morning, Rachel and Andrea are recorded as they form an agreement to produce crystal meth using a new technique with new chemical ingredients.

The following afternoon, Rachel and Andrea take delivery of the new chemicals; but before they begin mixing them, Officer Hank Schrader forces his way into the bunker and arrests them both for conspiracy to produce an illegal drug.

Scientific analysis later reveals that the chemical ingredients would have produced nothing more than harmless sludge. There was no possibility of them ever being capable of producing an illegal drug.

In that case, both Rachel and Andrea would be guilty of conspiracy to produce an illegal drug. The fact that they could not possibly have produced the drug is irrelevant.

An Agreement

Very rarely is it the case that the police are gifted with physical evidence of a conspiracy. Most criminals are sufficiently savvy to avoid writing down their plans in the form of a simple contract. As such, an agreement can be verbal; possibly even non-verbal. The extent to which a court would consider non-verbal actions evidence of a conspiracy is unclear, because the courts have not actually defined what an agreement is.

What we do know is that an agreement must be fairly specific. In R v Taylor (2002) D agreed with several others to import a class B drug into the UK. Or so he thought. What had actually been agreed upon was a plan to import a class A drug, and D had been confused about the nature of the agreement. The court held that D was not guilty of conspiracy to import a class A drug into the UK because he had not agreed to import a class A drug. Evidence of an agreement to import a class B drug is not evidence of an agreement to import a class A drug.

On the other hand, the courts will be prepared to overlook minor or irrelevant details if a general agreement has been reached. In R v Broad (1997) D agreed with P to import a class A drug into the UK. D thought he had agreed to import heroin, while P thought they had agreed to import cocaine. Both were found guilty of conspiracy to import a class A drug. The confusion about which specific class A drug was to be imported was an irrelevance.

It is vital to note that section 2(2) of the Criminal Law Act 1977 exempts certain people from the law of conspiracy:

  1. A spouse (husband or wife)
  2. A person under the age of criminal responsibility.
  3. The intended victim of the offence.

It is legally impossible for a married couple to form a conspiracy. If Mr and Mrs white form an agreement to murder their next-door neighbour, they are guilty of nothing more than being incredibly unpleasant neighbours. Similarly, if Mr White and his nine year-old son form a conspiracy to murder Mrs White, they are guilty of nothing more than being a desperately dysfunctional family.

Wheel and Chain Conspiracies

It is not necessary for all members of the conspiracy to talk to each other. In fact, members of a conspiracy might not know what their fellow conspirators look like, where they live, what their names are, what gender they belong to, how old they are, or how deranged they are. The conspiracy might be arranged by a “middle man” who hires conspirators separately (wheel conspiracy) or the agreement might be passed on by word of mouth: D1 tells D2, D2 tells D3, D3 tells D4 and so on (chain conspiracy). Consider the diagrams below (click to enlarge):

Wheel conspiracy

Wheel conspiracy

Chain conspiracy

Chain conspiracy


TaskConsider the following scenarios and decide which is an example of a wheel conspiracy, and which is an example of a chain conspiracy:

  1. Smith is a self-obsessed criminal whose main goal in life is to bolster his bank balance. Anybody who gets in his way ends up having their spines kicked through their hats. Smith decides that he wants to rob the Bank of England. The contacts list on his mobile phone consists of a variety of thugs and career criminals; so he starts to place phone calls. He hires Hogan to drive the getaway vehicle, Denning to control the staff, and Simmonds to launder the stolen cash.
  2. David has produced vast quantities of cocaine, which he wants to sell. He contacts his friend Daniel, who acts as distributor. In turn, Daniel contacts his friend Simon, who agrees to sell the drugs on the streets.

As a prosecutor, judge, or jury member, the key question is always the same:

What has to be ascertained is always the same matter: is it true to say…that the acts of the accused were done in persuance of a criminal purpose held in common between them? (R v Meyrick (1929))

Provided the answer to that question is yes, it does not matter whether the conspiracy comes as a wheel or a chain.

Mens Rea

Section 1(2) of the Act states the following:

Where liability for any offence may be incurred without knowledge on the part of the person committing it of any particular fact or circumstance necessary for the commission of the offence, a person shall nevertheless not be guilty of conspiracy to commit that offence by virtue of subsection (1) above unless he and at least one other party to the agreement intend or know that that fact or circumstance shall or will exist at the time when the conduct constituting the offence is to take place.

If we boil off the legal jargon, what we are left with is the following rule: Even if the crime agreed upon is one of recklessness or strict liability one cannot be guilty of conspiracy unless one intends to bring about that offence or knows that one will bring it about.

Consider the case of R v Saik (2006). In that case, D operated a bureau de change which – it was alleged – had been converting masses of stolen money into foreign currency: a clear example of money laundering. When he was charged with conspiracy to launder money, D accepted that he had suspected the money was stolen. We might say that he laundered the money with recklessness. On appeal, his conviction for conspiracy was quashed because he had not known that the money was stolen.

Does D Have to Intend That the Crime be Committed?

Looking at the Act, it is fairly clear that in order to be guilty of conspiracy, one must intend to form an agreement with at least one other person. But does the Act go further than that? Must D intend that the crime will be committed?

In R v Anderson (1986) D agreed with E and F to help break an inmate out of prison. For a payment of £20,000 he agreed to supply diamond wire, rope, ladders, and a safehouse. When D was charged with conspiracy, he argued that he intended to take the £20,000, supply only the diamond wire, and then run away to Spain. In effect, although he intended to agree with E and F, he did not intend to see the crime through.

The House of Lords in Anderson unanimously held that it was not necessary for D to intend to see the crime through. He had intended to form an agreement; the agreement had been formed; and the formation was enough to make him guilty of conspiracy.

The judgment in Anderson appears, at first glance, to be a victory for common sense. Something in our moral consciousness tells us that the defendant in Anderson had done something terribly wrong and deserved to be punished. But see if your opinion changes after taking-on the following task:


TaskConsider the ruling in R v Anderson and apply it to the following case:

Hank is an undercover police officer who has infiltrated a violent criminal gang which has been responsible for countless murders, and he is trying to gather enough evidence to put the gangsters on trial. One morning, in the local pool hall, Hank is invited to a meeting with Don Corleone and several of his henchmen. During the course of that meeting, the gangsters discuss a “hit” on a rival gang member and agree to shoot him dead the following day. Hank does not want to blow his cover or arouse suspicion, so he too agrees to the murder, although he intends to inform the police immediately after the meeting. As Hank is leaving the pool hall, the police raid the building and arrest the conspirators. Hank is charged with conspiracy to commit murder.

Since the ruling in R v Anderson states that D must intend to form an agreement, but does not have to intend that the crime ever takes place, Hank would be guilty. He intended to form an agreement and an agreement was formed. Although he might argue that he did not intend to see the crime though to its conclusion, this would be no defence, just as it was no defence for the defendant in Anderson.

The judgment in Anderson is clearly unsustainable and ill-considered. As a result, the Court of Appeal has ignored the Anderson decision on several occasions (Edwards (1991), Ashton (1992), Harvey (1999)).

In R v Edwards (1991) D agreed to supply E with amphetamine. He was convicted of conspiracy to supply a controlled substance but appealed his conviction to the Court of Appeal. The Court stated that in order to found a conviction for conspiracy to supply amphetamine, it must be proved that D intended to supply amphetamine. Since there was evidence to suggest that D actually intended to supply ephedrine instead of amphetamine, his conviction was quashed.

The decision by the Court of Appeal in Edwards clearly contradicts the decision of the House of Lords in Anderson. And although the judgments of the higher court ordinarily bind lower courts, it is suggested that the reasoning in Edwards, Ashton, and Harvey is the more accurate statement of law. The cases are more recent than Anderson, more reasonable, and more voluminous.

Although the law is far from clear, it seems likely that one must check the following boxes in order to have the mens rea for conspiracy:

  1. An intention to form an agreement which necessarily involves the commission of a crime.
  2. An intention that the crime be committed.

Intention to Play a Role in the Criminal Offence?

Is it possible for D to be guilty of conspiracy even though D does not intend to get involved in the crime? Even though D intends to play no part in the offence? Even though D is merely a silent partner?

Consider the case where D is a Mafia boss. He sits around a table with his fellow gangsters and makes a plan to rob the local bank. He gives several gangsters different jobs to do: drive the car, shoot the guards, break into the safe etc. The Mafia boss has one job, and one job only: to take a cut of the stolen money. Do you think that the law will let him get away with it? Or will he be guilty of conspiracy despite his lack of involvement?

In R v Siracusa (1989) the Court of Appeal stated that a conspiracy can be committed in one of two ways:

  1. D intends to actively participate in the crime (drive the car, shoot the guards etc).
  2. D intends to passively participate in the crime by failing to stop the unlawful activity.

In simple terms, D does not have to get involved in the substantive crime. If he has agreed that a crime should be committed, he is guilty of conspiracy. Full-stop.

Common Law Conspiracy

The Criminal Law Act 1977 explicitly retains two of the old forms of common law conspiracy:

  1. Conspiracy to defraud.
  2. Conspiracy to corrupt public morals.

The key case on conspiracy to defraud is Scott v MPC (1975) where Viscount Dilhorne described the offence as being:

An agreement by dishonesty to deprive a person of something to which is his or to which he is, or would be, entitled, and an agreement by two or more by dishonesty to injure some proprietary right of his.

Lord Diplock added that:

The purpose of the conspirators must be to cause the victim economic loss.

Let’s illuminate these statements of law by applying them to a case. In R v Cooke (1986) D was a British Rail steward who, along with some colleagues, took his own food and drink on-board a British Rail train and sold them as if they belonged to British Rail. D and his colleagues had agreed to deprive British Rail of the right to profit from food and drink sold on-board their trains; their purpose was to cause British Rail economic loss; therefore D was guilty of conspiracy to defraud.

The key case on conspiracy to corrupt public morals is Knuller (Publishing, Printing and Promotions) Ltd v DPP (1973). In that case, Lord Simon said that a conspiracy to corrupt public morals involves an agreement to carry out a course of conduct “which a jury might find to be destructive of the very fabric of society”.

Lord Simon’s intention was to limit the scope of conspiracy to corrupt public morals to those acts which are egregiously terrible, but the category is still incredibly broad. One of the principles of the rule of law is that the law should be relatively clear and unambiguous; it should be possible for ordinary citizens to discover what they can and cannot do under the law. And yet here we have a criminal offence whose scope depends entirely on the moral ideas of a jury of peers.

In Shaw v DPP (1962) D was the publisher of a magazine which detailed the names and addresses of prostitutes, along with descriptions of the sexual acts they were willing to perform. The House of Lords upheld his conviction for conspiracy to corrupt public morals.


  • Conspiracy is an inchoate offence.
  • It requires an agreement between two or more people.
  • It is not necessary for all conspirators to meet. The conspiracy might take the form of a wheel or a chain.
  • D must have an intention to form an agreement, and an intention that the offence be committed.
  • The agreement must be relatively specific.
  • D does not have to intend to play a role in the commission of the offence. He can be a silent partner.
  • Two categories of common law conspiracy prevail: conspiracy to defraud and conspiracy to corrupt public morals.

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