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Citation: Osland (1998) 159 ALR 170.

This information can be found in the Textbook: Brown et al, Criminal Laws: Materials and Commentary on Criminal Law and Process in New South Wales, (5th edition, Federation Press, 2011), pp. 987-992.


Background facts

  • Heather Osland and her son reached an agreement to murder Heather’s husband.
  • Heather mixed a sedative into her husband’s dinner and after he had fallen asleep, the son bashed him to death.
  • Heather was convicted of murder, but her son was acquitted. Heather argues in this appeal that her conviction is inconsistent with his acquittal, and she should be acquitted as well.

Legal issues


  • There are three types of offenders in a crime:
    1. Principles in the first degree - a person who commits acts which form the whole or part of the acts reus. Their liability is primary (regular liability), and there can be more than one principal in the first degree.
    2. Principles in the second degree - a person who did not commit any of the acts which form the acts reus, but was nevertheless present at the scene of the crime. Their liability is derivative, meaning that they can only be guilty if the principal in the first degree is convicted.
      • This means that they may benefit off the principals defenses such as lack of men's rea, provocation, self defence etc.
      • However, a principal in the second degree turns into a principal in the first degree if he had a pre-concert or agreement with the principal in the first degree to commit the crime. That means his liability becomes primary and he can no longer benefit from defenses used by the other principal in the first degree - his fate becomes irrelevant. This is what happens in a joint-criminal enterprise.
    3. Principles in the third degree - a person who committed none of the acts and was not present, yet aided in some way in the commission of the crime. They are accessories before the fact, and their liability is derivative, no matter what.
  • Distilling the principles mentioned above, and relying on Tangye[1], a person is a part of a joint criminal enterprise when the person did not commit the actus reus yet:
    1. Agreed with the others that they as a group will do the crime.
      • This does not need to be express and may be inferred from the circumstances. It also doesn't have to be made before the crime.
    2. Was present at the time of the crime.
  • In such a case, the actus reus committed by one or more of the parties will be attributed to to the persons deemed a part of the joint-criminal enterprise (ie, who satisfy the above test). Instead of being principals to the second degree, they become principals in the first degree. Each person is then independently of the mens rea findings of the other persons.
  • This is consistent with the concept of an “innocent agent” or a non-responsible party such as a child, mentally ill person or person under duress such as in R v Bourne (where a husband was found guilty of bestiality for compelling his wife to have sex with a dog).[2]
  • Of course, nothing stops those in the joint criminal enterprise to argue defences such as duress, provocation etc for their involvement in the joint criminal enterprise.
  • Accordingly, the acquittal of her son has no relevance on Heather Osland. It was his actus reus, and not his conviction as a whole, which was applied to her because of her part in the joint enterprise. Thus, she had the relevant actus reus, and also the mens rea (since she agreed to the crime). She is convicted irrespective of his trial outcome.


  1. (1997) 92 A Crim R 545.
  2. (1952) 36 Cr App R 125.
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