The judge, Mr Justice Mantell, warned them in his summing up at Winchester Crown Court that they must ignore the external pressures which the sensational character of the case had created.
"Nobody can pretend otherwise than that you have a heavy responsibility. Your task is not made any easier by the sensational nature of the case and by the very heavy media interest surrounding it," he said.
"I must repeat the warning to set aside all perceived ideas about the case, all prejudice and all sentiment. Cool heads are needed."
The judge told them that they must ignore what they had read in newspapers, seen on television or heard on the radio about the case.
Mrs West, 41, denies murdering 10 girls and young women whose remains were found at 25 Cromwell Street, Gloucester, where she lived with her husband Frederick, and at their previous home in the city. Mr West, who was charged with 12 murders, was found hanged in his prison cell last New Year's Day.
The judge told the jury: "The prosecution must prove guilt. A defendant never had to prove his or her innocence ...
"Guilt is not proved unless the prosecution makes you sure of it. In other words, the prosecution has to satisfy you beyond reasonable doubt that that applies to each and every charge.
"Murder is the deliberate unlawful killing of another human being with the intention at that time to cause death or really serious bodily harm. It is not just the person who strikes the fatal blow who is guilty. Where two people act together as part of a joint plan to commit the offences each is guilty.
"Suppose you were sure that Rosemary West had enticed a young woman to Cromwell Street ... then even though it might be that Fred West was ultimately responsible for despatching the victim Rosemary West would be equally guilty."
The judge told the jury not to "speculate about what evidence there might have been. You have heard all the evidence".
The judge will continue his summing up today and the jury is expected to be sent out to consider its verdicts on Monday.
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