An Adelaide man died from a toxic cocktail of drugs including morphine, valium and tramadol which had all been prescribed to his partner, a court has been told.
NSW woman Wendie-Sue Dent is on trial in the South Australian Supreme Court charged with the murder of her de facto husband David Lawrence in December 2015.
Prosector Emily Telfer SC told the jury on Monday Mr Lawrence's death was not the result of suicide or an accidental overdose.
"This was a deliberate killing by the accused of David Lawrence because she stood to gain financially from his death," Ms Telfer said.
The prosecutor said a post mortem examination had found traces of all three drugs in the dead man's blood and traces of those drugs were also present in a glass of orange liquid found next to his bed.
An expert would tell the court the level of morphine found in the 63-year-old's system was the equivalent of him taking 20, 100-milligram tablets.
Ms Telfer told the jury that after the death of Mr Lawrence, Dent, who was brought from Dapto in NSW to face trial, had tried to portray their relationship in such a way as to maximise her chances of benefiting financially.
Dent had also produced some typed and hand-written documents, including a will, which indicated Mr Lawrence wanted all his estate to go to her, including about $300,000 in superannuation.
The court heard phone intercepts and a listening device placed in Dent's home in Dapto detected her telling other people he had asbestosis or was suffering from terminal cancer.
Ms Telfer said those claims were untrue.
But in an opening statement, defence counsel Stephen Apps told the jury Dent's life fell apart after the death of Mr Lawrence and she had "grabbed at any other possible cause of death".
He said in a state of denial she had told some untruths but did not intend to harm her loved one in any way.
Dent, he said, had shared her own medication with Mr Lawrence at his request to help ease his back pain.
Mr Apps said the defence would submit that Mr Lawrence died from an accidental overdose.
The trial continues.