Jurors in the trial of murder-accused nurse Lucy Letby have been told to approach the case in a “fair, calm, objective and analytical way”.

Letby, 33, is accused of murdering seven babies and trying to murder 10 others during the course of her work on the neonatal unit at the Countess of Chester Hospital.

The defendant, from Hereford, is said to have seriously harmed and killed the babies in various ways, including by injecting air intravenously and administering air and/or milk into the stomach via nasogastric tubes.

She also allegedly added insulin as a poison to intravenous feeds, interfered with breathing tubes and used force to the abdomen.

Some of the babies, the prosecution say, were subjected to repeated attempts to kill them.

On Thursday, June 15, trial judge Mr Justice James Goss gave his first set of directions of law to the jury of eight women and four men ahead of the prosecution and defence delivering their closing speeches at Manchester Crown Court from next week.

He told jurors, who were sworn in last October, they should decide the case solely on the evidence placed before them.

He said: “As I said at the very beginning of the trial, you must not approach the case with any pre-conceived views and you must cast out of your decision-making process any response or approach to the case based on emotion or any feelings of sympathy or antipathy you may have.

“It is instinctive for anyone to react with horror to any allegation of deliberately harming, let alone killing a child – the more so a vulnerable premature baby.

“You will naturally feel sympathy for all the parents in this case, particularly those who have lost a child and the harrowing circumstances of their deaths.

“You must, however, judge the case on all the evidence in the case in a fair, calm, objective and analytical way – applying your knowledge of human behaviour, how people act and react, using your common sense and collective good judgment in your assessment of the evidence and the conclusions to be drawn from it.”

Mr Justice Goss told jurors it was not their role to “resolve every conflict in the evidence”.

He said: “It would, you may think, be a remarkable and exceptional case in which a jury could say we know everything about what happened in any case and why.

“You are not detectives.

“If you are sure that someone on the unit was deliberately harming a baby or babies, you do not have to be sure of the precise harmful act or acts. In some instances there may have been more than one.

“To find the defendant guilty, however, you must be sure that she deliberately did some harmful act to the baby the subject of the count on the indictment and the act or acts was accompanied by the intent and, in the case of murder, was causative of death.”

He told the jury they also did not need to certain of any motive for deliberately harming a baby.

Mr Justice Goss said: “Motives for criminal behaviour are sometimes complex and not always clear. You only have to make decisions on those matters that will enable you to say whether the defendant is guilty or not of the particular charge you are considering.

“Any decision you do make must be based on evidence and not speculation.”

Turning to the subject of “circumstantial evidence and the unlikelihood of coincidence”, he said this was a case in which the prosecution “substantially, but not wholly” rely upon circumstantial evidence.

Mr Justice Goss went on: “The defendant was the only member of the nursing and clinical staff who was on duty each time that the collapses of all the babies occurred and had associations with them at material times, either being the designated nurse or working in the unit.

“If you are satisfied so that you are sure in the case of any baby that they were deliberately harmed by the defendant then you are entitled to consider how likely it is that other babies in the case who suffered unexpected collapses did so as a result of some unexplained or natural cause rather than as a consequence of some deliberate harmful act by someone.

“If you conclude that this is unlikely then you could, if you think it right, treat the evidence of that event and any others, if any, which you find were a consequence of a deliberate harmful act, as supporting evidence in the cases of other babies and that the defendant was the person responsible.

“When deciding how far, if at all, the evidence in relation to any of the cases supports the case against the defendant on any other or others, you should take into account how similar or dissimilar, in your opinion, the allegations and the circumstances of and surrounding their collapses are.

“The defence say that there are possible causes for many of the collapses other than an intentional harmful act, that the prosecution expert evidence cannot be relied on in terms of providing explanations for many of the collapses and that there is insufficient evidence to lead you to the conclusion that these events were related and were a consequence of any harmful act by the defendant rather than a series of unrelated collapses that, in some cases, ended in death.”

When considering the seven counts of murder, Mr Justice Goss told jurors they must be sure Letby deliberately did something to the child that was “more than a minimal cause” of the death.

He said: “The children were all premature and vulnerable, some had mild respiratory distress syndrome of prematurity and some had specific health issues.

“There were also a few cases of delays in the administration of appropriate medicine or other clinical failings. Some of the causes of death were unascertained.

“In the case of each child, without necessarily having to determine the precise cause or causes of their death and for which no natural or known cause was said to be apparent at the time, you must be sure that the act or acts of the defendant, whatever they were, caused the child’s death in that it was more than a minimal cause.

“The defendant says she did nothing inappropriate, let alone harmful to any child. Her case is that the sudden collapses and death were, or may have been, from natural causes or for some unascertained reason or from some failure to provide appropriate care, and they were not attributable to any deliberate harmful act by her.”

Letby denies seven counts of murder and 15 counts of attempted murder between June 2015 and June 2016.

The trial continues on Monday, June 19.

The Standard will have liver coverage of the closing speeches.