R v Kopsch – Case Summary

R v Kopsch (Alfred Arthur)

Court of Appeal

Citations: (1927) 19 Cr App R 50.


The defendant killed a woman by strangling her with his neck-tie. He told police that she had asked him to strangle her as part of a sex act. He later claimed that this belief, and his actions, were due to a mental condition he was suffering from. This condition was said to have instilled in him an irresistible, subconscious impulse. The defendant was convicted of murder.

  1. Is an irresistible impulse from a defendant’s subconscious sufficient to fulfil the requirements of the insanity defence?

The Court of Appeal upheld the conviction. The insanity defence was not established.

This Case is Authority For…

If the defendant knew his actions are illegal, and knew the nature and quality of his acts, the defence of insanity is inapplicable. It does not matter that the defendant was acting under a subconscious or irresistible impulse when carrying them out.


The Lord Chief Justice in this case seemed disbelieving that there was such thing as an irresistible impulse. He also thought it would be subversive to the criminal law to acknowledge it.

Does this align with modern understandings of mental illness?