I REFER to the debate in the Letters Pages on the issue of assisted suicide (March 31, April 1 & 2) and in particular the letter from Professor James Chalmers published on April 2.

He asserts that the law of causation in Scotland is unclear and therefore the law relating to assisted suicide is unclear. This is not the case.

As I set out in detail in a letter dated May 21, 2014 to the convenor of the Health and Sport Committee of the Scottish Parliament, the applicable law for assisted suicide is the law of homicide. The law relating to homicide is clear and accessible. Murder is constituted by any wilful act causing the destruction of the life of another, by which the perpetrator either wickedly intends to kill or displays wicked recklessness as to whether the victim lives or dies. Where the intention for murder cannot be proved (including where the offender's responsibility is diminished) then the crime is culpable homicide.

Prof Chalmers raised the issue of causation. The law relating to this is clear. In order for there to be a sufficient causal connection for homicide the conduct must be a significant contributory factor to the death. A minimal or negligible contribution would not suffice. This clear test, which has persisted for many years, will be applied to the facts and circumstances of each case.

Thereafter where there is sufficient credible and reliable evidence consideration would have to be given to whether prosecution is in the public interest. The criteria for deciding this is set out in the Scottish Prosecution code which is publicly available on the the Crown Office and Procurator Fiscal Service (COPFS) website. I would add the obvious point that given the seriousness of the crime of homicide - it is the most serious crime in the Law of Scotland - it is difficult to conceive of a case where it would not be in the public interest to take proceedings, but each case would be considered on its own facts and circumstances.

If proceedings are taken it would be a matter for the jury to consider whether they were satisfied to the criminal standard of proof that the accused was guilty of homicide. If convicted it would be for the court to decide on sentence.

In a democracy it is important that changes to the law of assisted suicide are decided by the Scottish Parliament and not by me in the issue of prosecutorial guidance. Prosecutorial guidance cannot change the law or remedy a defective law. That would be unconstitutional and an affront to the rule of law. If members of the public want the law of this country relating to assisted suicide changed they need to persuade a majority of MSPs to do this.

Rt Hon Frank Mulholland QC,

Lord Advocate,

The Crown Office, 25 Chambers Street, Edinburgh.