Letby, 33, from Hereford, is accused of murdering seven babies and attempting to kill 10 others on the neonatal unit of the Countess of Chester Hospital.

She allegedly pumped air into the circulation of several of her victims, which is said to have led to air embolisms in which gas bubbles can block blood supply.

Letby submitted a clinical incident report stating that on June 30 2016 she noticed a bung had been left off the port of an intravenous line, which could accidentally let air in.

The shift was her last on the unit before she was moved to clerical duties after consultants raised fears to hospital bosses about her presence at a number of collapses, Manchester Crown Court heard.

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Days earlier, two triplet boys who she had been caring for had collapsed and died.

In his closing speech to the jury of eight women and four men, prosecutor Nick Johnson KC said: “It is Lucy Letby, we say, getting her defence in first. She knew the net was closing.

“Text messages showed she knew there was going to be an investigation.

“She put in a form that contained a lie and the purpose of putting this in is to create the impression that air embolism could have arisen on the unit as a result of poor practice.

“It is a calculated attempt by a devious woman to deflect suspicion.”

Mr Johnson told jurors they could be sure the report timed at 3pm was false because Letby would have started her shift at 8am and any nurse doing their job properly would not take that long to spot the issue.

When giving evidence, Letby denied the prosecutor’s claim the report was effectively an “insurance policy to cover yourself for accidental air embolism”.

Letby, from Hereford, denies all the allegations said to have taken place between June 2015 and June 2016.