He can't cry, kick his legs or breathe unassisted. His body is growing; his brain is not.

Baby Charlie Gard, three weeks shy of his first birthday, suffers from a rare degenerative disorder. There is no cure. He's being kept alive on a ventilator at a renowned children's hospital in London, where doctors want to take him off life support to allow him to "die with dignity." 

But Charlie's parents are in a bitter legal fight to try one last experimental treatment in the U.S. that they know won't save his life but which they say might at least improve it.

"He wakes up, he enjoys his tickles, we lie next to him," said his mother, Connie Yates.

"If he was suffering, I couldn't do it. I promise you."

Charlie Gard

Charlie has mitochondrial depletion syndrome, which saps his muscles and organs of energy. He has brain damage and cannot move or cry. The disease is considered fatal. (Facebook)

But whether or not he's suffering is one of the many disputed facts in this case. Doctors say prolonging his life is causing suffering and that no existing treatment can save him. 

The Pope, U.S. President Donald Trump and a variety of lawyers, ethicists and doctors have all weighed in on the British baby's fate. As Charlie lies mute in hospital, an impassioned debate swirls around what rights parents have to control their children's medical care.

Kaylom Hoppe-Carlie-Gard-protest

Kaylom Hoppe, 5, leads chants to 'save Charlie Gard' outside London's Court of Justice, which is hearing evidence in the Gard case Thursday. (Susan Ormiston/CBC)

Two previous courts have ruled with the doctors at London's Great Ormond Hospital. The case is now being heard at Britain's Supreme Court. Under British law, in the rare case when a dispute arises over a child's treatment, a hospital can take it to the courts to decide.

Justice Nicholas Francis was expected to rule on the case Thursday morning but delayed the decision until the court can hear from the U.S. doctor who would administer the experimental treatment the family is seeking, called nucleoside bypass therapy.

The doctor is expected to testify via video later this morning.

On Monday, in an emotional, high-spirited hearing before the court, Francis ruled the parents had until Wednesday to deliver new evidence of treatment they believe could benefit their son.

Experimental drug therapy

"I'm still fighting for the same thing that I've been fighting for since November 2016," said Charlie's mother. 

Even a 10-per-cent chance of improvement, at best, is "a good enough chance to take oral medication with no major side effects," she says.

A health-care facility in the U.S. has agreed to care for the baby and administer the experimental treatment. It is not curative, but the family's lawyers argue it could slightly improve the baby's underlying condition.

Chris Gard and his nearly one year old

Charlie's father determined to get his baby to the U.S. for an experimental treatment called nucleoside bypass therapy that won't save his life but that the parents think could improve his condition. (Charlie Gard Facebook )

Born healthy, Charlie's muscles began to fail around six months. Doctors discovered he had inherited the faulty RRM2B gene that inhibits cells from making energy and had mitochondrial depletion syndrome. His current care team says subsequent seizures in January caused irreparable brain damage. His parents disagree.

"I've yet to see something that tells me my son's got irreversible structural brain damage," said Yates.

Other children on medication 'getting stronger'

She told the BBC that other children with Charlie's condition are currently on the experimental medication.

"They all have mitochondrial depletion syndrome as well as Charlie, but theirs is caused by a slightly different gene. They're all getting stronger."

"This isn't about the parent's right to control what happens to their child," said Penney Lewis, co-director of the Centre of Medical Law and Ethics at Kings College London.

Gard Protest

Protesters stand outside a London court to show support for Charlie and his parents. (Reuters)

"Parents don't have that right, [but] they do have a responsibility to take care of their child as best they can.

"I think one of the things that seems so heartbreaking is that the parents really believe that he could be saved, that he could have a much improved quality of life, and that doesn't appear to be what the evidence suggests."

Support for petition, crowdfunding 

Yates and Charlie's father, Chris Gard, have used social media to their advantage to spread the word and to crowdfund enough money on GoFundMe for them to travel to the U.S. for treatment. More than 400,000  people have signed a petition calling on doctors to allow the baby to travel to the U.S. A Facebook page has been charting the legal steps in the case, and an American Christian group protesting euthanasia has arrived in London promoting #IamCharlieGard on Twitter.

The world's most high-profile tweeter, U.S. President Trump, interjected his opinion on Monday: "If we can help little #CharlieGard, as per our friends in the U.K. and the Pope, we would be delighted to do so."

'I think sometimes one loses sight of a very, very unwell child. Because it becomes a kind of political circus in some sense.' - Penney Lewis, bioethicist

Then on Wednesday, U.S. Vice-President Mike Pence used the case to make a political point in the U.S. health-care debate. Speaking to Rush Limbaugh on radio, Pence said the baby Gard case is evidence the "single payer" system of medicine doesn't work.

"The mother and father should be able to choose the lifesaving treatment that's available ... instead of submitting to a government program, which says, 'No, we're going to remove the life support from your precious 11-month-old child.'"

Doubts over treating 'very unwell child'

But the experimental treatment will not save Charlie's life, argue many top physicians in the U.K. If it would, doctors at Great Ormond wouldn't hesitate to administer it.

"I think it is disturbing to watch," Lewis said in an interview with CBC News. "I think sometimes, one loses sight of a very very unwell child. Because it becomes a kind of political circus in some sense."

Britain's top pediatrician, Neena Modi, wrote in an open letter, "Charlie's situation is heartbreaking for his parents, and difficult for everyone, including the doctors and nurses looking after him."

She said the interventions from high-profile figures are "unhelpful."

But as Charlie lies in his tiny hospital cot, with round-the-clock care, his parents believe all the international attention has "saved his life so far."

"We're not strong people, but what is strong is the love for our little boy," said Chris Gard. "He's kept us going through all of this."