Despite her long work days, she always found time to help around the house. She cooked, led a prayer group and went to church every Sunday, usually arriving early enough to snag one of the front pews.

“My mother always wanted me to be more like her,” Renji Thomas said of Ms. Joseph. “She was so loved, and she became like a sister to me.”

Ms. Joseph’s mother in-law, Annamma Thomas, a former schoolteacher, kept the house buzzing, tutoring children and hosting big dinners for family and friends, as well as an annual Christmas party that was the biggest in town.

But after a few years, they began clashing over money, according to family and friends. Annamma was in charge of the family accounts.

In 2002, five years after Ms. Joseph had moved into the family home, Annamma died a painful death. She had been unwell, and one day, Ms. Joseph urged her to sit down and relax, promising a warm bowl of goat soup to ease her churning stomach. Investigators say the soup was laced with cyanide. Annamma collapsed and died, frothing at the mouth.

The Christmas parties grew smaller and eventually stopped. Friends and family stopped coming by, feeling the house had grown cold under its new matriarch, Ms. Joseph, said Mohammed Bava, a neighbor who lives across the street.

He said Tom Thomas, Ms. Joseph’s father-in-law, became reclusive after his wife’s death.

“He became very sad and silent, and increasingly came under Jolly’s control. He stopped interacting with all of us,” said Mr. Bava, who grew up playing in the Thomas household.