Health authority bosses have asked Mr Justice Hayden to consider whether continuing ''active'' treatment is in best interests of the retired steel worker - who is in his 80s.
The judge is analysing the case at a public hearing in the Court of Protection (a part of the High Court, above) - where issues relating to people who lack the mental capacity to take decisions are heard - in London, which is expected to end later this week.
Medical experts said the pensioner has suffered ''catastrophic'' brain damage and has a life expectancy measured in months.
Treating doctors fear that he is experiencing pain but no pleasure.
But the man's daughter told Mr Justice Hayden on Tuesday how she thought that he was improving and would want to carry on living.
She said: "He loves life. It is important to him - the sanctity of life.
"We have to leave it up to God.
"We know dad is not going to get back like he was but I firmly believe that his remaining days will be happy.
"He knows that we are with him and he gets pleasure from our company."
