A woman and her husband shot dead her elderly parents after her mother bragged about sleeping with her husband, a court heard.
Susan Edwards, 55, and her husband Christopher, 57, are accused of shooting her parents William and Patricia Wycherley and burying them in the back garden in Forest Town, Mansfield.
They deny murder but have admitted to wrapping them in bedding and burying them under the lawn of the Mansfield home during May Day bank holiday weekend in 1998.
The couple were exhumed last year after the authorities wanted to congratulate Mr Wycherley on turning 100.
Mrs Edwards admits shooting Mrs Wycherley, but she said she did this after discovering that her mother had killed her father before boasting she had had an affair with her husband, Christopher, Nottingham Crown Court heard.
The jury was also told the couple installed timers so neighbours thought the couple were alive for almost 15 years and sent Christmas cards to relatives for years and pretended to be the Wycherleys - stealing £245,000 from their accounts including from their pensions.
In a 2007 letter, Susan Edwards told a relative Christmas cards to her parents had been returned because the couple had moved to Ireland to enjoy the 'good air'. They had been dead for nine years.
The debt-ridden couple's web of deceit was only unravelled when the authorities wanted to interview William Wycherley and congratulate him on his 100th birthday.
Prosecutor Peter Joyce QC said: "They deceived and tricked everyone into believing that Susan Edwards' parents, William and Patricia, were still alive.
"They could then cover up the killings and continue to fund their own lifestyle and help to solve their financial difficulties out of monies that were continuing to be paid to the Wycherleys."
By 2007 they owed £160,000 to creditors when they were eventually arrested last October.
The elderly couple's bodies were exhumed in the back garden of their home in 2013.
The trial continues.