Lucy Letby was one of only two nurses on duty when two baby boys were deliberately poisoned with insulin, a court has been told.
The nurse, 33, denied attempting to murder the days-old infants in “targeted” attacks nine months apart.
Giving evidence for an 11th day, Letby accepted someone must have laced the boys’ feeding bags with insulin, but denied it was her.
Prosecutor Nick Johnson KC told the jury on Monday that only two nurses worked both shifts when the infants were allegedly poisoned, Letby and a colleague named Belinda Simcock.
“Isn’t the reality that unless there’s more than one poisoner, it has to be either you or Belinda Simcock?” Johnson asked.
Letby replied: “I can only answer for myself and say that I’ve never put insulin into any bags.”
Johnson said: “It was never suggested to be her [Simcock] though, was it?”
The defendant responded: “I can’t answer that.”
Letby, originally from Hereford, denies murdering seven babies and attempting to kill another 10 at the Countess of Chester hospital between June 2015 and June 2016.
The prosecution alleged that the nurse attempted to murder two premature baby boys, Child F and Child L, by poisoning them with insulin.
She allegedly targeted seven-day-old Child F less than 24 hours after murdering his twin brother on 4 August 2015.
She is accused of attempting to murder two-day-old Child L, another twin, nine months later on 9 April 2016.
The jury has been told that blood test results for both boys showed extremely high insulin levels and very low C-peptide levels, which the prosecution says is “conclusive evidence” they were poisoned.
Letby said she did not know who gave the boys insulin or how.
“Whoever did it, did it deliberately, didn’t they?” Johnson asked.
Letby replied: “If it happened on the unit, yes.”
Johnson continued: “We’ve already established it happened on the unit – it’s sometime between midnight and half-nine in the morning in that bag that was connected to [Child L] the whole time.”
Letby responded: “Yes, apart from the cannula was replaced.”
The prosecutor said: “That’s why it’s a targeted attack, isn’t it?”
Letby, sat between two prison officers, did not answer. After Johnson asked, “What do you say?” she eventually replied: “Not by me it wasn’t.”
The crown alleges that Letby injected insulin into a total parenteral nutrition bag that she hung for Child F along with another nurse who cannot be named for legal reasons.
Letby said she could not say whether Child F had been deliberately poisoned “because I don’t know how insulin got there or who put it there or why”.
The jury has been told that the poisonings were not spotted at the time because the blood-test results emerged only months later.
Johnson said Letby was not asked about the alleged insulin murders until her second police interview, in June 2019, almost a year after her first arrest.
The trial, now in its 31st week before a jury, continues.
