I genuinely don’t know how I feel about this.
A person’s lucidity, once they have started treatment for a life ending condition, will vary from person to person and asking someone who hasn’t spent much time with that person to determine whether or not they are lucid enough to request assisted death, would be, imo, wrong.
I think the primary care giver, ie the specialist doctor who has been treating the patient, should be front and centre in helping to determine lucidity and to give a clear view of the patient’s life expectancy and quality of life, should treatment continue.
From the moment my wife started to receive treatment for her cancer diagnosis, her mental capacity was impaired, partly due to the radiotherapy to her brain, partly due to the relentless chemotherapy and partly due to the painkillers she was prescribed.
Even during the short periods of remission, she was still taking strong painkillers that “dulled” her thought processes, so she was never as sharp and precise in her thinking as she had been before the treatment had begun.
My wife rejected morphine for as long as she could, having seen how it had affected her mum’s brain, but when the pain became too much to bear she started to take liquid morphine, along with a variety of other medications, which led to her having hallucinations as well as further dulling her thought processes.
So, bearing in mind what I witnessed with my wife, I could lean towards someone being able to make the decision up to 12 months before their anticipated death, simply because their thought processes might be more coherent than they would be 6 months down the line when their body and mind has been further hammered by medication.
BUT I think there would need to be provisos in place to ensure that they can change their mind and to prevent them from making a decision that has been forced upon them.