Criminal Law


This topic looks at Re (A) (Children) (Conjoined Twins: Surgical Separation), which was a Court of Appeal decision on the separation of conjoined twins that took place in September 2000. The decision of the three judges in Re A was a matter of life or death which required them to grapple with difficult issues of legal principle, policy, ethics and morality.

A Summary of the Case

The Facts

Two girls were born as conjoined twins; they were joined at the pelvis. Medical evidence suggested that if the girls were not separated they would both die before they were one year old. If they were separated then it was likely that the stronger one, Jodie, would survive, but the weaker one, Mary, would certainly die.

Although the issue for the Court of Appeal was simply whether or not the surgery should be allowed, this required them to consider the criminal law. This was because, if the operation took place, the surgeon might be guilty of murder. If he would commit that offence then the operation could not be authorised by the court.


The crime of murder is committed where:

(1) a person (known as the defendant) has caused the death of the victim; and

(2) the defendant intended to kill or to cause serious injury to the victim. Intention will be established either where:

(i) the defendant’s purpose is to kill or to cause serious injury (known as direct intention); or

(ii) the defendant foresaw death or serious injury as a virtually certain consequence (known as oblique intention).

Even where the defendant causes death and intends to kill or to cause serious injury, he or she will not be guilty of murder if he or she has a defence. English law recognises the following defences, amongst others:

(a) Private defence: defence of oneself or another from actual or threatened attack. This applies where the defendant acts reasonably to save him or herself or another person from harm. Traditionally the defence will only be available where the defendant or another person is attacked or about to be attacked by the victim.

(b) Duress of circumstances. This applies where the defendant or another person is subject to a threat of death or serious injury. This defence has not previously been applied where the defendant has been charged with murder.

(c) Necessity. This applies where the defendant commits one crime to avoid greater harm. However, this defence has not been recognised as a defence to murder.

The Issues

The key issues for the Court of Appeal concerned whether, if the surgery was performed and Jodie died, the surgeon would be guilty of murder. In particular:

(i) whether the surgeon could be considered to have intended to kill Mary by performing the operation; and

(ii) if so, whether the surgeon would have a defence, particularly whether the defence of necessity, in the sense of acting for the greater good, should be extended to the crime of murder.

Now read through the texts in the activity resources, watch the videos from Professor Graham Virgo and then consider the questions below. 

Video Resource

Video Resource

Video Resource

Resource activities

Considering the Criminal Law Issues

What principles of law need to be considered here? Read about these as well as the views of two Lord Justices.


Considering the Welfare Issues

How can we assess the welfare issues involved? Read through the assessment from Lord Justice Ward.


Activity questions

  • If you were a judge in this case would you order the surgical separation to take place, knowing that one of the twins would definitely die?
  • If the twins were separated and one died, could you say that the surgeon had caused the death of that baby and that the surgeon intended to kill the baby?
  • Should the surgeon have a defence to murder? If so, what should it be?
  • Is it relevant that the parents of Jodie and Mary did not want the surgery to take place?
  • A and B are rock-climbing. They are tied together by a rope and are near the top of a rock-face. B falls and is hanging from the rope. A cannot hold onto the rock-face for much longer. A cuts the rope and B falls to his death. How would you deal with this problem?
  • A and B are in a lifeboat without any food and water. B is close to death. A kills B and eats him. A is rescued. How would you deal with this problem?
  • A is awaiting an urgent heart transplant and has only days left to live. B is suffering from a terminal illness and is close to death. C, a doctor, kills B and transplants his heart (which is unaffected by the illness) in A’s body. How would you deal with this problem?

Reflective questions

To answer and record these questions you will need to have an account and be logged in.

Task 1

What are the key arguments, concepts, points contained within it?

Task 2

What are you struggling to understand?

What could you do to improve your understanding of these concepts/terminology etc.?

Task 3

What further questions has this resource raised for you?

What else are you keen to discover about this topic and how could you go about learning more?

Can you make any links between this topic and your prior knowledge or school studies?

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Further reading

  • Nicklinson Case

    It may be argued that certain cases on euthanasia should also be able to enjoy the defence of necessity. A landmark case on this is the Nicklinson case.

  • Homicide Law Reform

    Another issue raised by the conjoined twin case is whether the existing law on murder and its possible defences are satisfactory.