The prosecution says Letby, 33, from Hereford, inflicted an injury to the infant and also injected him with air while he was under her care at the Countess of Chester Hospital.

Letby denies the murders of seven babies and the attempted babies of 10 others on the neonatal unit between June 2015 and June 2016.

She is said to have targeted her fifth alleged victim, Child E, during a night shift in August 2015.

Letby is also accused of attempting to his murder his twin brother, Child F, by poisoning him with insulin.

Manchester Crown Court has previously heard from a prosecution medical expert that a rigid wire or tube may have been used to cause “extraordinary bleeding”.

Child E deteriorated from 11.40pm on August 3, the court heard, and later died early the next morning having lost a quarter of his blood volume.

The boy’s mother had told the court that she heard “horrendous crying” as she visited her son at 9pm and then saw blood around his mouth.

Letby says no bleeding took place prior to 10pm.

Prosecutor Nick Johnson QC asked: “Is it your case that medical incompetency contributed to his collapse or death?”

Letby replied: “Possibly, yes.”

Mr Johnson said: “Whose medical incompetencies?”

Letby said: “The medical team who were on that night.

“I just think collectively they could have acted sooner to respond to the blood issue.”

Mr Johnson said: “Their reaction would be dependent on when you told them there was a bleed?”

“Yes,” said Letby.

Mr Johnson said: “The prosecution case is that (Child E’s mother) is telling the truth and (Child E) was bleeding at 9pm.

“But you didn’t tell anyone about that until at least an hour later?”

Letby said: “No I disagree with that.

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“I think once (Child E ) was profusely bleeding after 10pm maybe a blood transfusion or something could have been given sooner.

“I don’t know if that would have made a difference.”

Letby said it would have been the decision of the duty consultant, registrar and senior house officer that night to have made the decision to prescribe and give a blood transfusion.

Mr Johnson went on: “I am suggesting to you that when (Child E’s mother) came down at 9pm you had inflicted an injury on (Child E) to cause bleeding?”

Letby said: “No, I don’t accept that. It didn’t happen.”

Mr Johnson said: “That’s why he was screaming, wasn’t it?”

“No,” said Letby.

Mr Johnson said: “Did you tell (Child E’s mother) that the source of the bleed was the insertion of a nasogastric tube?”

Letby said: “No.”

Mr Johnson said: “That is what you told (Child E’s mother) when she queried why he had blood around his mouth?”

Letby said: “No, I don’t recall that, I don’t believe I would have said something like that.”

The defendant denied the suggestion that she had “falsified records” including when failing to record a vomit of fresh blood on an observation chart.

Letby said: “It was an error on my part but it was in my nursing note.”

Mr Johnson said: “Or was it in the excitement of sabotaging (Child E) you overlooked it?

“No.”

Mr Johnson said: “You killed (Child E), didn’t you?”

“No,” said Letby.

Mr Johnson said: “And you injected him with air.”

“No,” said Letby.

Mr Johnson said: “Just as you had done with other babies before?”

Letby repeated: “No.”

Mr Johnson asked: “Why in the aftermath of were you so obsessed with (Child E’s mother)?”

Letby said: “I don’t believe I was obsessed with (Child E’s mother).

Mr Johnson said: “Why were you searching for her continually on Facebook?”

Letby replied: “Because I often thought about (Child E) and (Child F).

The court has heard the defendant searched for Child E’s mother on nine occasions, including on the late evening of Christmas Day 2015.

Mr Johnson said: “Didn’t you have better things to do on Christmas Day?”

Letby said: “I often thought of (Child E) and (Child F).”

Mr Johnson said: “Because you had killed one and had tried to kill the other.”

Letby said: “No I didn’t.

“I thought that myself and (Child E’s mother) had a good relationship.”

Letby, from Hereford, denies all the allegations.