They loved 79-year-old Suzine Van Sickle and brought her back home to live out her days, they said.
But Van Sickle's caretakers - her daughter and granddaughter - yesterday were convicted of poisoning, then smothering her.
A King County jury found Jimmie Jean Shumway, 59, the daughter, and Alexis Shumway, 29, guilty of premeditated first-degree murder in the bizarre killing last November that they kept secret for three months.
The two showed no emotion as the verdict was read yesterday.
Deputy Prosecutor Lisa Marchese said that after the two depleted the $100,000 estate of the widowed Van Sickle, she no longer was useful to them.
"They got rid of the burden," the prosecutor said in closing arguments. "They murdered her."
The daughter and granddaughter gave separate statements to police telling how they had chopped up 50 capsules of Dilantin, an anti-seizure medicine, then mixed it in clam chowder and fed it to Van Sickle Nov. 17 in the family home in Rainier Valley.
But when she was still alive the next day, they put a pillow over her face and suffocated her. After a 20-minute struggle, Van Sickle died.
A medical examiner concluded she died of congestive heart failure, and her body was donated to the University of Washington.
"This was the perfect murder - with the one exception - a guilty conscience," John "Jay" Mooney, a Seattle homicide detective, said after the verdict.
Alexis Shumway, who was chief caretaker for her grandmother, lived with the secret until Feb. 12, when she called police.
Marchese and Deputy Prosecutor Kerry Keefe brought evidence showing that the daughter, after getting power of attorney for her mother in late 1987, wrote 30 checks to herself totaling $45,000.
More than $13,000 was donated to the Church of Scientology, the prosecutors said. Payments to the nursing home where Van Sickle previously lived were overdue.
Police found a paper in Jimmie Jean Shumway's Federal Way home where she had written the fatal dosage for Dilantin - two to five grams - after consulting the Physician's Desk Reference.
The daughter said in her statement, "I did it. It was a mercy killing." She said Van Sickle several times had talked about taking her own life.
The granddaughter's statement said she held the pillow "for a while, then I just held my grandmother's hand."
When Van Sickle was killed, the fees to the nursing home where she earlier resided were $33,000 in arrears and the establishment was attempting to put a lien on her home on South Brandon Street.
Juror Carla Anderson said after the verdict:
"I think we all were concerned about Alexis. We felt that her mother obviously dominated and that she was passive."
But the jury had no choice but to follow the law, she said.
Superior Court Judge Frank Sullivan will sentence the two in about six weeks. The standard sentencing range is 20 to 26 years in prison.
Neither has a criminal record.