The Court of Appeal hearing in the case of 12-year-old Archie Battersbee, who is at the centre of a life-support treatment dispute is due to start this morning.
A High Court judge concluded the youngster was "brain-stem dead" and ruled that doctors could lawfully stop providing treatment.
Archie's parents are now bringing an appeal against that decision. The case will be livestreamed via the Court of Appeal's website.
Doctors treating Archie at the Royal London Hospital in Whitechapel, east London, had previously told Mrs Justice Arbuthnot they think he is "brain-stem dead".
They said treatment should end and Archie should be disconnected from a ventilator.
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Archie's parents, Hollie Dance and Paul Battersbee, of Southend, say his heart is still beating and want treatment to continue.
Lawyers representing the Royal London Hospital's governing trust, Barts Health NHS Trust, asked Mrs Justice Arbuthnot to decide what moves were in Archie's best interests Mrs Justice Arbuthnot concluded Archie is dead, and said treatment should end, but gave Ms Dance and Mr Battersbee permission to mount an appeal.
She said there is a "compelling reason" why appeal judges should consider the case.