R v Cox – Case Summary

R v Cox

Crown Court

Citations: [1992] 12 BMLR 38.


The defendant was a doctor who had treated the victim for over 13 years. The victim’s arthritis made her life unbearable and was terminal. She asked the defendant to end her life. The defendant gave her an injection of potassium chloride. It was unclear whether she died of her condition or the injection. As such, the defendant was charged with attempted murder.

To secure a conviction, the prosecution had to show that the defendant intended to end the patient’s life. The defendant argued that he did not have this mens rea. This was because, he argued, he was administering the drug to relieve pain, not to kill. He sought to rely on the doctrine of double effect. This exonerates medical professionals who accelerate death in order to relieve pain.

  1. Did the defendant have the appropriate mens rea for attempted murder?

The judge directed the jury that double effect only applies if the defendant’s primary purpose was to relieve pain. Death had to be merely an incidental consequence of this. The jury convicted the defendant of attempted murder. This indicated that they found that the defendant’s primary purpose was to cause death.

This Case is Authority For…

A doctor cannot rely on the doctrine of double effect where their primary purpose is to end life. Their primary purpose must be to relieve pain, where death is merely incidental.


This case indicates that where the drug administered has no inherent pain-relieving qualities, a doctor will not succeed in showing that their primary purpose was to relieve pain rather than kill.