A TEN-WEEK-OLD boy who died after he collapsed at home with his father was a victim of shaken baby syndrome, a court heard.

Harry Barnes was shaken so severely part of a bone in his neck broke off, Britain’s top pathologist told a jury.

Dad Christopher Barnes was alone with his son when the infant collapsed at the family home in June 2017.

He denies manslaughter and grievous bodily harm.

Home Office pathologist Dr Nat Cary carried out an extensive post mortem at Great Ormond Street Hospital after the death of baby Harry.

Other experts were called in to help examine specific details of his death and Dr Cary presented his conclusions to the jury at Lewes Crown Court.

Shaking had caused the injuries which lead to cardiac arrest and the fatal brain damage which killed the baby, he said.

The pathologist, who has worked on some of the most high-profile cases in recent history, said the infant died after at least two shaking incidents.

Barnes, 28, listened intently from the dock as the jury was taken through the post mortem.

From examination of Harry’s eyes, experts found there had been head trauma from movement, impact or a combination of both, after vigorous movement in the torso, Dr Cary said.

A complete fracture through a neck bone was also the result of shaking, Dr Cary added.

“In terms of shaking injury, this is towards the severe end of the spectrum.

“Most likely due to so-called shaken baby syndrome. The forces involved were severe and towards the upper end.”

The pathologist said it was not unusual in similar cases for there to have been an earlier, non-fatal incident of shaking.

The fatal event would have occurred close to the time the emergency services were called, he said.

Sally Howes, for Barnes, said there would be no way to demonstrate in court how a baby would need to be shaken in order to recreate the injuries found during the post mortem.

“To cause this sort of injury would be in excess of rough handling,” Dr Cary said.

“Babies have design flaws, including a large head and weak neck”, Ms Howes said.

“The second design fault is the part of the head which gives the life-preserving functions is located at the bottom of the brain.”

“Exactly,” Dr Cary agreed.

“A young baby is more vulnerable to this than an older baby.

“An eye-witness account would be the best way to determine what had happened to baby Harry?” Ms Howes asked.

“Yes,” Dr Cary agreed.

“How long is the lag phase between a shaking event and cardiac arrest?”

“It wouldn’t be very long,” the pathologist said.

He could not say for certain if the fatal event had happened within hours or minutes before an ambulance was called to the family home in Midhurst.

Harry Barnes collapsed on June 24, 2017 and died the next day after life-support was withdrawn.

Heating engineer Christopher Barnes denies manslaughter and causing grievous bodily harm.

The trial continues.