"This is within the bounds of reasonableness," said Professor David Dennison, a consultant clinical physiologist, on the second day of an appeal by Jenkins, 41, against his Lewes Crown Court conviction and life jail sentence for murdering Billie-Jo, 13, at the family home in Hastings, East Sussex.
The jurors who convicted the former deputy headmaster of bludgeoning Billie-Jo to death with a metal tent spike last year had been told by scientific experts for the prosecution that the 150 tiny blood spots could only have resulted from his being close to the girl as she was being struck.
They said Billie-Jo would not have been alive 15 minutes after the attack when Jenkins claimed to have discovered her.
Professor Dennison told the Appeal Court hearing that a post-mortem report showed that Billie-Jo's lungs were "hyper-inflated", indicating a blockage in the airways such as a blood clot in the nasal valve. If that blockage were suddenly removed, air would be expelled through the nose, carrying blood with it.
He did 120 experiments over three months, using apparatus simulating the nasal cavity and found that a fine spray of blood, invisible to the naked eye, could be produced by 4 per cent of the volume and 7 per cent of the force suggested by the prosecution. The appeal continues.