A 17-month-old boy who is at the heart of a landmark right-to-life case, has an "intolerable life", the High Court heard today.
The boy, MB, suffers from spinal muscular atrophy - an incurable and progressively worsening condition leading to complete paralysis.
He cannot breathe for himself, cannot chew or swallow, is fed through a tube and - while not impaired mentally - can only move his eyebrows, feet, and his fingers very slightly.
A hospital trust has asked Mr Justice Holman for permission to withdraw life-saving ventilation from the child because he has such a low quality of life.
It is believed to be the first time that such a move has been taken in the case of a patient who is sentient and not in a persistent vegetative state.
His parents, from the north of England, want their son to live.
They feel he can recognise and respond to them and has enjoyment from spending time with his family, and this gives him a reasonable quality of life.
There is a court order in place preventing the identification of any of the parties in the action.
Questioned by Caroline Harry Thomas, counsel representing the child's interests, a Dr S told the court today: "One has to consider his inability to move and his inability to communicate effectively, his inability to express his wishes, his inability to show if he is in any pain or distress or, if he is, what is causing that.
"I think the cumulative effect of all of that is that he has an intolerable life."
The doctor said that if the current treatment regime continued, the child would be unlikely to die before he got to the point over the passage of several months where he would be unable to open his own eyelids.
He would need them opened manually to be able to see.
If treatment continued - and despite high-quality nursing care - he would also develop pressure sores, require an increased level of oxygen at a higher pressure and develop scoliosis.
The child had been wearing splints on his hands and feet intermittently, which caused discomfort, and a risk of limb fractures would develop in relation to normal handling.
MB's parents, who are expected to give evidence later today, were in court.
His mother has said: "We want our son to have a tracheotomy so we could take him home and give him a life instead of him being stuck in a hospital cubicle.
"We are very hopeful we can persuade the court that his quality of life is good enough so that treatment should not be withdrawn."
Miss Harry Thomas asked Dr S if his evidence was that because of the child's "lack of ability to show response", it was not possible to "fine tune" his sedation and pain relief.
The witness told the court: "I think it is very difficult to fine tune in terms of the sedation and pain relief.
"We are in a very difficult position because on one hand we are concerned about the distress that he is going through, so it is appropriate to give sedation to try and minimise that.
"If you give it at a dose that means he is essentially asleep all the time, then that does not feel to me to be an acceptable situation for him.
"On the other hand if we decrease the sedation we do not want to decrease to a level that means he is in an unacceptable level of distress and discomfort."
Charles Foster, counsel for the family, asked Dr S if "future hypothetical detriments" had weighed heavily on him in deciding that continued ventilation would be futile.
Dr S replied: "That was part of it, but it was also where we are now that has weighed heavily on me."
Mr Foster suggested to him that the application before the court "is premature by many months and possibly by many years".
The doctor responded: "I would disagree with that statement.
"I would actually say that it could be seen as an application that is later than it should have been."
He said that all the experts in the case, including those instructed by the family, had attended a meeting and were of the view that a planned withdrawal of ventilation was in the child's best interests.