Prosecutors have asked the Netherlands' Supreme Court to clarify legal matters in a landmark euthanasia case, saying Thursday they want to lay down unambiguous jurisprudence for the future.

The Public Prosecution Service said by instituting "cassation in the interest of the law" proceedings they aim to clarify how doctors deal with euthanasia on "incapacitated patients" without subjecting a doctor acquitted at a trial to a new legal battle.

Prosecutors said in a statement they want "legal certainty to be created for doctors and patients about this important issue in euthanasia legislation and medical practice."

The retired nursing home doctor was cleared earlier this month by judges in The Hague who ruled that she adhered to all criteria for carrying out legal euthanasia when she administered a fatal dose of drugs to a 74-year-old woman with severe dementia.

The cassation proceedings mean that the doctor's acquittal will not be called into question.

The doctor carried out euthanasia on the woman in 2016, acting on a written directive the patient had drawn up earlier. The woman later gave mixed signals about her desire to die, but the doctor, in close consultation with the woman's family, decided to go ahead with the mercy killing.

The Hague District Court ruled that in rare cases of euthanasia on patients with severe dementia - and who had earlier made a written request for euthanasia - the doctor "did not have to verify the current desire to die."

Prosecutors said they disagreed with the Hague court and want the Supreme Court to rule on legal issues in the case.