A baby died in extreme pain during her final collapse under the care of murder-accused nurse Lucy Letby, a court heard.
The 33-year-old is accused of murdering the girl, referred to as Child I, at Countess of Chester Hospital in October 2015.
Ms Letby denies murdering seven babies and attempting to murder 10 others.
Dr Sandy Bohin told the trial at Manchester Crown Court, the baby's crying was "inconsolable" as the court heard Ms Letby made three attempts to kill the baby before succeeding on the fourth attempt.
Dr Bohin told Nick Johnson KC, prosecuting, that in her opinion Child I's death was caused by air being injected into her bloodstream.
Baby boy has spent his life in hospital as doctors are 'scared' to discharge himShe said one of the reasons for her conclusion was that Child I was very distressed at the time of her final collapse.
Dr Bohin said: "Nurses get a sense of why babies are crying" and added the baby's crying was "very different".
She added: "This was inconsolable crying, which is extremely unusual. [Child I] was in pain and must have been in extreme pain to be that distressed."
When cross-examined by Ms Letb's defence, Ben Myers KC, Dr Bohin denied that she was "rubber stamping" the earlier report by another prosecution expert, Dr Dewi Evans.
Mr Myers said: "We don't know what your conclusion would have been if you'd not been provided with Dr Evans's report first?"
Dr Bohin replied: "That's correct, but my duty is to give an independent review and that's what I've done."
A mother of another baby girl allegedly harmed by nurse Lucy Letby said she was "utterly shocked" at her sudden collapse, a court heard.
The court was told Child I was born prematurely in August 2015 at Liverpool Women's Hospital at the gestational age of 27 weeks and weighed 2Ibs 2oz (970g).
She was transferred to the Countess of Chester Hospital later that month.
In a statement read to the court, Child I's mother said her daughter was about six weeks old when she thought the infant might be well enough to go home.
Disabled woman paralysed after falling from wheelchair on plane walkway diesShe said: "I started to notice that she was looking different. She was looking around the room now, taking it all in.
"I was able to sit her on my knee. I remember looking at her and thinking, 'we are going home'.
"She looked like a full-term baby, she didn't look frail or small."
The trial continues