The family of a man found stabbed to death in a Southwest Philly backyard last month says they still don't know what caused his girlfriend to allegedly take his life.

But a sister of 30-year-old Quinton Graham, of Kensington, who was found stabbed to death on Aug. 8, said 34-year-old Dionia James deserves the harshest possible punishment for the crime.

"I want her to do life. It was first-degree murder," said Chantee Graham, Quinton's sister.  

James waived her right to a preliminary hearing on first-degree murder charges Tuesday in the hopes that waiving the hearing might provide a "tactical advantage" to future negotiations for pleading to a reduced charge from the Philly D.A.'s office, her attorney Samuel Stretton said, although nothing is guaranteed.

James, who wore a pink shirt in court, said little in court except to tell the judge she agreed with her attorney's advice.

James is charged with stabbing Graham to death on Aug. 10 in a backyard in Grays Ferry near Oakford and 27th streets.

Graham's sister Angel Graham said the killing took place in the backyard of James' husband's sister — and that afterwards, James called Chantee and Angel, telling them that someone was laying in her backyard and she didn't know if it was Quinton or not.

Later James claimed Quinton was murdered during an attempted robbery, his sisters said -- but instead, detectives arrested and charged James with the crime.

Stretton was not immediately available to comment on Graham's family members' accusations.

Chantee, Angel and their aunt Gwen Lewis credited the Philadelphia Police Department's detectives with quickly solving the murder, but said Graham's children, a son and daughter aged 13 and 10, are still grieving.

"You just have to pray," Angel said. "All these senseless killings is just sad. People have children, they have families. You're ripping them apart."