The parents of brain-damaged Archie Battersbee, 12, have been given permission to appeal against a court ruling that his life support should be stopped.
A judge last week ruled that Archie was dead but the case is now set to be considered by the Court of Appeal.
Archie suffered brain damage after his mother found him unconscious at their home in Southend, Essex, on 7 April. He hasn't regained consciousness since.
It is thought he may have been taking part in an online challenge.
Doctors believe he is "brain-stem dead" and should be disconnected from a ventilator at the Royal London Hospital.
However, his parents want the treatment to continue and say his heart is still beating and he has gripped his mother's hand.
At the High Court today, their barrister, Edward Devereux QC, said evidence must show beyond reasonable doubt that Archie is dead, rather than using a balance of probabilities test.
He also said the judge had not taken into account the religious views of Archie and his family.
Mr Devereux outlined a number of other grounds of appeal, but eight of the nine were dismissed as being without merit.
These included that the court had erred in extending the common law definition of death to include brain stem death, and that its analysis of best interests was flawed.
Lawyers representing the Royal London Hospital's governing trust, Barts Health NHS Trust, asked judge Mrs Justice Arbuthnot to decide what was in the boy's best interests.
The legal fight will now continue after she gave Archie's parents, Hollie Dance and Paul Battersbee, approval to start an appeal and said the standard of proof issue was a "compelling reason" why the higher court should look at the case.
Archie parents are being backed by the Christian Legal Centre.
Andrea Williams, its chief executive, said: "A ruling that says death can be declared on the balance of probabilities sets a troubling precedent for our society and must be appealed.
"This case is the first of its kind in an English court and has raised significant moral, legal and medical questions as to when a person is dead.
"Archie's parents believe that the time and manner of his death should be determined by God and claim a right to pray for a miracle until and unless that happens. That belief must be respected."