NURSE Lucy Letby told detectives any deliberate dose of insulin given to a twin baby boy was “not done by me”, her murder trial heard.

Letby, 33, is accused of intentionally poisoning the youngster while on duty at the Countess of Chester Hospital’s neo-natal unit.

The Crown say she harmed the infant on April 9, 2016 and also on the same day caused the sudden collapse of his brother who stopped breathing as his oxygen levels and heart rate dipped.

Both boys went on to recover and were discharged home the following month, Manchester Crown Court was told.

When later interviewed by Cheshire Police following her arrest Letby denied deliberately administering insulin to Child L, who cannot be identified for legal reasons.

She said to her knowledge neither she nor a nursing colleague had accidentally administered the substance, which had not been prescribed.

Letby added she could not believe such a mistake would have been made.

When suggested by detectives it was a deliberate act of sabotage, the defendant replied: “That was not done by me.”

Asked if she had any explanation for the presence of insulin in Child L’s circulation she said it “must have been in one of the bags or fluids he was receiving”.

Earlier, Dr Anna Milan, a consultant clinical scientist at Royal Liverpool Hospital said a blood sample from Child L sent to its lab by the Countess of Chester showed the insulin was “exogenous”.

The readings confirmed it was given to the patient rather than being naturally produced by the pancreas, she told the court.

The results were later communicated by phone to the Countess of Chester’s biochemistry lab on April 14.

Jurors were also told that three vials of insulin were issued to the neo-natal unit in 2014, six vials in 2015 and two vials in 2016.

Insulin was kept in a locked fridge in an equipment room but the keys for access would be passed between nurses on duty as and when required, the court heard.

Letby, originally from Hereford, is also accused of attempting to murder another youngster, also a twin boy, with the administration of insulin in August 2015.

She denies the murders of seven babies and the attempted murders of 10 others between June 2015 and June 2016.

The trial continues on Tuesday, February 21.