The process to select a jury to try Benjamin Field, 28, and Martyn Smith, 32, began at Oxford Crown Court on Tuesday before High Court Judge Mr Justice Sweeney.
A panel of 27 potential jurors was whittled down to 21, of whom 12 will be sworn in to hear the case.
Field, a church warden, and Smith, a magician, deny involvement in the deaths of Peter Farquhar, 69, and Ann Moore-Martin, 83, who lived three doors away from each other in the picturesque village of Maids Moreton in Buckinghamshire.
Detectives launched a murder inquiry more than two years after the death in October 2015 of Mr Farquhar, a guest lecturer at the University of Buckingham, and seven months after the death of retired headmistress Ms Moore-Martin in May 2017.
Field and Smith deny charges of murdering Mr Farquhar and conspiracy to murder Ms Moore-Martin. Field also denies an alternative charge of attempting to murder Ms Moore-Martin.
The pair deny two charges of conspiracy to defraud and a single charge of possession of an article for use in fraud.
Field, of Wellingborough Road, Olney, Buckinghamshire, has pleaded guilty to four charges of fraud and two offences of burglary.
Smith, of Penhalvean, Redruth, Cornwall, denies three charges of fraud and two offences of burglary.
Tom Field, 24, of Wellingborough Road, Olney, Buckinghamshire, faces trial accused of a single charge of fraud.
The trial was adjourned until Thursday.
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