A woman who killed her 2-year-old granddaughter by tossing her off an elevated walkway at Virginia's largest shopping mall was motivated by hatred of her son-in-law for getting her daughter pregnant out of wedlock, prosecutors said Monday.

Defense lawyers, meanwhile, acknowledged that Carmela Dela Rosa, 50, of Fairfax, tossed her granddaughter, Angelyn Ogdoc, off the sixth-level pedestrian bridge but said she was mentally ill and legally insane at the time.

A jury in Fairfax County heard opening statements Monday at Dela Rosa's murder trial. She faces up to life in prison.

Commonwealth's Attorney Ray Morrogh told the jury that Dela Rosa was a hateful, self-centered woman who never got over the fact her daughter got pregnant out of wedlock, and she harbored such a deep hatred for her son-in-law that she was willing to kill her own granddaughter to exact revenge.

The two-week trial will look "deep into the dark side of a human heart," Morrogh told the jury of nine men and five women, including two alternates.

Morrogh said Dela Rosa calmly explained to detectives what she did and why she did it just a few hours after the Nov. 29 incident at Tysons Corner Center, in the midst of the busy holiday shopping season, and that she concocted her plan well before she acted out, while she dined on kebabs and frozen yogurt during an extended family outing at the mall's food court.

"She had a reason that she felt justified in what she did, and I submit it's consistent with her personality," Morrogh said.

Dela Rosa remained bitter toward her son-in-law, James Ogdoc, for getting Mary Kathlyn Ogdoc pregnant in 2007. The two married in 2008, before Angelyn was born. But Morrogh said Dela Rosa, a deeply religious Catholic who immigrated from the Philippines as a teenager, continued to blame James Ogdoc for tearing her family apart.

"She was mad at the world and her place in it," Morrogh said. "But mostly what stuck in her craw was the bitterness she felt toward James Ogdoc."

Morrogh's statement to the jury was the first time authorities ever discussed a motive in Angelyn Ogdoc's death.

Dela Rosa's public defender, Dawn Butorac, disputed prosecutors' version of events and said Dela Rosa loved her family, especially young Angelyn.

"She loved Angelyn. She doted on her. She spoiled her," Butorac told the jury.

Dela Rosa suffered from major depressive order and had twice tried to commit suicide in the months before Angelyn's death _ once by taking 75 prescription and over-the-counter pills, and once by driving into a steep ravine in the scenic Shenandoah Mountains.

In the days leading up to the incident, Dela Rosa had been left alone by her family and was spiraling downward badly, refusing to shower or eat.

Butorac said Dela Rosa's depression was so severe that she was having psychotic thoughts, and that mental health experts conclude that she met Virginia's legal definition of insanity, which requires that Dela Rosa either could not distinguish right from wrong, or did not understand the nature and consequences of her action.

Morrogh, though, argued that at most Dela Rosa was depressed and that she knew what she was doing. He said that she slowed down when exiting the mall with Angelyn so that she trailed far enough behind the rest of the family that nobody would be able to run back and stop her.

"She did it out of anger, hatred and revenge," Morrogh said. "There were no hallucinations. There were no delusions. She was not schizophrenic."

The prosecution's first witness, mall patron Monique Cox, testified that she was walking into the mall with her fiance when she heard some shouts and saw what she thought was a child's jacket falling to the ground.