The parents of a baby with a rare disease stormed out of a London court hearing in an emotional outburst Thursday, as the couple tried to convince a judge to let them take their critically-ill child to the United States for medical treatment.

Charlie Gard’s parents are challenging the view of Britain’s most famous children’s hospital, arguing that treatment abroad is in the best interest of the 11-month-old suffering from a rare genetic condition.

A succession of judges has backed specialists at Great Ormond Street Hospital, who argue experimental treatment in America won’t help and may cause suffering for Charlie. The parents hoped to present fresh evidence to alter that view.

Two hours into the High Court hearing, questions from Judge Nicholas Francis prompted tensions to boil over. Charlie’s mother, Connie Yates, accused Francis of misquoting her earlier statements about Charlie’s quality of life.

“We said he’s not suffering and not in pain,” Yates yelled. “If he was we wouldn’t be up here fighting.” Chris Gard then slammed his water cup down and the couple left the courtroom.

Charlie suffers from mitochondrial depletion syndrome, a rare genetic disease that has left him brain damaged and unable to breathe unaided. The hospital says there is no known cure and believes his life support systems should be turned off.