A woman used her lover as a hitman to murder the father of her children, a jury has heard.
Crown lawyer Ciaran Murphy QC told Coleraine Crown Court that Hazel Stewart, 47, was part of a plan which she helped execute to sacrifice the life of her policeman husband and kill her then lover's wife with carbon monoxide fumes.
He added the killings were a joint enterprise, a plan executed by dentist Colin Howell and Stewart to rid themselves of their respective spouses for them to be together.
Mother-of-two Stewart's defence lawyer Paul Ramsey said she was guilty of perverting the course of justice and withholding information, but was innocent of murder.
But Mr Murphy claimed she could have stopped the killing.
"If she had an inkling of humanity for her husband, she would have intervened at that point, if she had any thought for him at all. She chose not to," he said.
Stewart, from Ballystrone Road, Macosquin, Coleraine, who has denied the two murders, sat impassively in the dock as Mr Murphy urged the jury to find her guilty in his closing submission.
Her husband, Pc Trevor Buchanan, 32, and Lesley Howell, 31, the wife of her lover, were found dead in a car filled with carbon monoxide fumes in a garage behind a row of houses known as the Twelve Apostles in the seaside town of Castlerock, Co Derry, in May 1991.
At first, police thought they had died in some sort of suicide pact because of the distress over their spouses' affair.
It was only when Howell, 51, first confessed to his church elders and then police in January 2009 that he had murdered them that Stewart was arrested by investigating detectives.