Prosecutors said the couple had indirectly but significantly contributed to the child’s death because their prolonged abuse and neglect had considerably weakened her immune system and ability to fight the bacterial infection.

The children’s 56-year-old step-grandmother has denied all four counts of child cruelty she has been charged with.

None of the defendants or their relatives can be named due to a gag order from Mr Justice Albert Wong Sung-hau aimed at protecting the identity of the children.

Forensic pathologist Dr Kwok Ka-ki said she found 58 recent injuries and 75 scabbed wounds, ulcers and scars when she performed an autopsy on the deceased on January 9, 2018.

The expert concluded the fresh injuries were compatible with recent blunt force trauma caused by slapping and punching, as well as objects such as a rattan stick, clothes hanger, slippers and scissors.

In particular, she found there were deep confluent bruises all over the child’s scalp and that some of them were inflicted within one to two days before death.

Kwok said the head injuries were compatible with blunt force trauma and could be caused by bumping against a hard surface. She agreed with the prosecution’s suggestion that it could be caused by throwing the child towards the ceiling.

Couple deny murdering daughter, 5, who died after months of ‘torture in hell’

The court previously heard from the girl’s brother and stepsister, who similarly recalled seeing their father repeatedly throw her in the air, with her head hitting the ceiling in the process, while their mother was said to have watched and encouraged him, on the night before she died.

But the mother’s defence counsel, Caesar Lo, questioned: “Would you expect more serious injury?”

“This is already quite serious to me,” Kwok replied.

Meanwhile, the father’s counsel, Alex Ng, noted that the child had a normal height and weight, and was not malnourished.

“From the outside, she looked normal,” Ng continued. “The injuries we found were only visible when the deceased was lying naked to you on the autopsy table.”

Kwok countered that the injuries on the girl’s face were “quite obvious” and pointed out that there was visible swelling on her arm.

But she agreed with the defence that there could be other explanations for some of the injuries, such as her falling on the ground or bumping against the edge of a table.

She also noted that none of those injuries were fatal and concluded that the cause of death was septicaemia – a severe form of bacterial infection – after finding salmonella enteritidis in the deceased’s bloodstream, which had spread to many organs.

Her expert report also revealed that the girl’s thymus – an important organ for child immunity – weighed only five grams, while that of a normal healthy child under the age of 10 would weigh between 16 and 40 grams.

The court also heard from senior forensic pathologist Dr Foo Ka-chung, who examined photographs of the boy, taken by hospital staff upon admission on January 6, 2018.

Baby with head injury sparks child-abuse investigation in Hong Kong

Foo said the different stages and unusual sites of the multiple bruises shown were indicative of abuse, while the scabbed wounds suggested they “should have been inflicted for a prolonged period of time”.

He also found there were 10 scars on the boy’s chest which were consistent with poking by a pair of scissors, as the child had claimed.

The photos also captured a black necrotic ulcer on the boy’s right buttock, which Foo said was a deep and chronic wound possibly inflicted months ago by multiple trauma, such as repeated beating with a slipper.

Foo said these injuries “definitely” required attention by medical professionals as they could affect the child’s normal life.

For instance, the ulcer on his bottom would make it difficult for him to sit properly, while the injuries on both legs could affect walking.

“A lot of pain will be inflicted on [the boy],” Foo said.

The trial continues.