As you say, we see physician-assisted dying as part and parcel of compassionate end-of-life care. Our position is that it should be treated no differently from withdrawing or withholding treatment or providing palliative sedation.
If a patient—for example, an individual who is suffering from ALS—wanted assistance to die with dignity, we would expect that they would make their desire known to their doctor and that their doctor would make sure they were fully informed of all their available end-of-life options. We would expect that they would be fully informed about their prognosis and their diagnosis, etc., and were made aware of the existence of palliative care and other options available to them. This is in keeping with standard medical practice.
A doctor may have a pre-existing relationship of over a decade or more with a patient and may know the patient's views well, but if the doctor had any concerns about the patient's capacity, any concerns about the patient's ability to make an informed voluntary decision free from duress, keeping in mind that in many situations those concerns won't exist, the doctor would then, in keeping with normal medical practice, refer that individual for an individualized capacity assessment. That could mean referring the patient to another doctor or to a psychiatrist or a specialist in geriatrics. There are a variety of ways in which doctors are able to seek capacity assessments.