Cases in which the victim had a clear and informed desire to end their life or in which the suspected killer acted under significant emotional pressure could make prosecution unlikely.

In its updated homicide guidance the CPS addresses mercy killings and failed suicide pacts. The new guidelines seek to help prosecutors determine the public interest in such cases and whether or not to prosecute.

Mercy killings are those in which a life is taken to alleviate suffering. Failed suicide pacts are those in which one person survives an agreement between two people to die together.

Max Hill KC, Director of Public Prosecutions, said: “We have made a number of changes to our guidance, but it doesn’t follow from that that I’m predicting fewer cases going to court or fewer charges of murder.”

He stressed that “it is murder to kill another person even when you are carrying out the wishes of another person”.

He added: “So my strong message is that the public interest in charging homicide cases and taking them to court is very high and remains so even after we publish this guidance and there are going to be circumstances, even going through the extra content of the code, where a prosecutor should conclude that the case will go ahead and any consideration of mercy is for the court and not the prosecution.”