Nurse Lucy Letby is on trial accused of the murder of seven babies and the attempted murder of 15 more.
Letby, of Arran Avenue, Hereford, denies murdering five boys and two girls, and attempting to murder another five boys and five girls between June 2015 and June 2016.
She was working in the neonatal unit of the Countess of Chester Hospital in Chester at the time.
Here are the key developments from her trial on Monday 10 October.
'Poisoner at work' Opening the prosecution case, Nick Johnson KC said the Countess of Chester Hospital was a “busy general hospital” which included a neo-natal unit that cared for premature and sick babies. He said: “It is a hospital like so many others in the UK but unlike many other hospitals in the UK, and unlike many other neo-natal units in the UK, within the neo-natal unit at the Countess of Chester Hospital a poisoner was at work.”
'Common denominator' Mr Johnson continued by saying that the babies had deteriorated unexpectedly. Those that didn't die had recovered unexpectedly quickly, he said. Mr Johnson told the court that "one common denominator" linked the deaths, and that was "the presence of one of the neo-natal nurses and that nurse was Lucy Letby".
Staffing numbers Mr Johnson said that the number of nursing staff at the Countess of Chester’s neo-natal unit was between 25 and 30 nurses, along with about 15 nursery nurses.
'No accident' Mr Johnson said that many of the events in the case occurred on the night shifts. However, he said, that when Letby was moved to day shifts, the collapses and deaths "moved to the day shifts". Jurors were shown a chart showing nurses who were present on duty when the alleged criminal incidents were said to have taken place. Pointing out, as examples, the first three alleged offences in time he said the chart showed the only person that was present on all three occasions was the defendant.
'Malevolent presence' The collapses and deaths of all the 17 children concerned were not “naturally-occurring tragedies,” Mr Johnson said. “They were all the work, we say, of the woman in the dock, who we say was the constant malevolent presence when things took a turn for the worse for these 17 children.” Mr Johnson said the two children poisoned with insulin, who cannot be identified, were two baby boys, both born twins; the first born in summer 2015 and the other born in spring 2016. Both were poisoned a couple of days after they were born.
'Causes of death' Mr Johnson said sometimes babies were injected with air and on other occasions they were fed with insulin or too much milk. He told the court: “So varying means by which these babies were attacked but the constant presence when they were fatally attacked or collapsed catastrophically was Lucy Letby.” Mr Johnson said in the case of the two babies injected with insulin, identified only as child F and child L, their blood sugar levels dropped to dangerous levels.
Child A Mr Johnson then turned to each individual case, starting with child A in which he alleged the following events took place: Child A, a baby boy, was born at 8.31pm on June 7, 2015; he was born early, by C-section, at 31 weeks, and admitted to intensive care; by the following day, he was in good condition; Letby came on to work on the night shift at 7.30pm for the handover; at 8pm, Letby became the designated nurse for child A; at 8.26pm she called a doctor to the baby’s incubator and the on-call consultant was also alerted; both doctor and consultant noted an “odd discolouration” on the child’s skin; despite resuscitation attempts, child A was pronounced dead at 8.58pm, within 90 minutes of Letby coming on duty.