London (CNN) -- A jury in the case of two former personal assistants accused of defrauding celebrity chef Nigella Lawson and her ex-husband Charles Saatchi was sent out Thursday but has not yet reached a verdict.
Francesca Grillo is accused of defrauding Lawson and Saatchi of 580,000 pounds ($950,000), and Elisabetta Grillo is accused of defrauding them of 105,000 pounds ($172,000). They deny the charges.
The jury was sent home for the night and will resume deliberations Friday.
One of the defendants was not in the dock at the end of deliberations Thursday because "she is not feeling well," the judge said.
The Italian sisters have told Isleworth Crown Court in west London that Lawson authorized their personal expenditures on Saatchi's company credit cards, including on designer shoes, clothes and trips abroad.
Their respective defense lawyers said in their closing arguments Thursday that the prosecution's claims had not been proved.
They also argued that for the jury to return a guilty verdict, it would have to be sure that Lawson did not authorize the sisters' spending either explicitly or implicitly.
Both defense lawyers questioned Lawson's credibility as a witness and said their clients' claims that she repeatedly used drugs were relevant to that issue.
Elisabetta Grillo's defense lawyer, Anthony Metzer, told the jury that his client was the "soft underbelly" by which Saatchi was attacking Lawson after the breakdown of their relationship. The couple divorced this year.
Karina Arden, representing Francesca Grillo, said her client had made no attempt to hide her spending, so it was impossible for Lawson to say she was ignorant of it.
The case has gripped UK media, thanks to revelations of drug use by Lawson and intimate insights into her troubled marriage to Saatchi, a millionaire art collector.
Jane Carpenter, giving the prosecution's closing argument in the case, said Thursday that the sisters had abused their position "time and time again" and that they "grew bolder and greedier" as time went by.
"Just because Saatchi is a wealthy man, obviously it doesn't mean he should be defrauded by the staff," Carpenter said. "That seems to be what the defense are putting forward."
She urged the jury to find both sisters guilty.
In her own testimony, Lawson confirmed she had taken cocaine half a dozen times, during two periods of her life, and used cannabis in the past. But she denied being a habitual user.
The court heard that none of the witnesses had seen her take drugs.
Lawson, whose culinary skills and flirtatious manner have long entranced UK audiences, has also appeared as a judge on the ABC show "The Taste" in the United States. A second season of the show is due to air in January.