Such wills could be overturned if the subject’s mental capacity is subsequently questioned, meaning that a doctor must assess them at the time they make their decisions.
The judgment, handed down by Mr Justice Peter Jackson in the Court of Protection last week, concluded that a 32-year-old woman, identified only as “E”, who has not eaten for a year should be given life-saving treatment against the wishes of both her and her family.
Paul Bowen, QC, of Doughty Street Chambers, who acted for the local authority in the case, said of the ruling: “It should be a word of caution to people who suffer from conditions that can deprive them of capacity, where it fluctuates.
“They should have psychiatric assessments (before making an advanced directive) – it’s not enough just to sign it in front of family members, otherwise courts may set them aside.”
Adam Wagner, a barrister at One Crown Office Row, said: “From reading the sensitive and carefully reasoned judgment, this was clearly an extremely difficult and complex case.
“What is clear from Mr Justice Jackson’s ruling is that advance directives require a ‘full, reasoned and contemporaneous assessment evidencing mental capacity’.
“The judge found that despite E and her mother having reasons to believe E had capacity, this was not enough. A formal capacity assessment at the time was required in order to show that E had capacity to make such a momentous decision.”