Published: May 15, 2014 12:29 PM EDT

TAMPA, Fla. (AP) - Prosecutors and defense attorneys gave jurors opposing arguments Thursday over whether a Tampa military mother was legally sane when she fatally shot her two teenage children three years ago.
Prosecutor Jay Pruner told jurors in his closing arguments that Julie Schenecker, 53, murdered her 16-year-old daughter Calyx and her 13-year-old son Beau because she was afraid her Army officer husband was about to divorce her and she didn't want to be alone.
The teens were shot to death while her now ex-husband, Parker Schenecker, was on a 10-day deployment to the Middle East as an Army colonel.
Her attorney, Jennifer Spradley, argued that Schenecker was legally insane when she shot the children and didn't know right from wrong.
If convicted of first-degree murder, Schenecker, a former Army linguist, faces a mandatory life sentence as prosecutors aren't seeking the death penalty. If acquitted by reason of insanity, she would be committed to a mental hospital until doctors and a judge agree that she is no longer a danger to herself or others.
During his 30-minute argument, Pruner laid out why he believes Schenecker knew what she was doing, including the detailed planning she had undertaken.
"Focus on the state of mind of the defendant at the time of the offense. That is the critical time frame," he said.
Pruner told the jury that Schenecker was "desperate, depressed, angry, but very determined." He said she was despondent over what she thought was the inevitability of divorce.
"These were deliberate, well planned, well implemented and well concealed homicides," Pruner said.
He showed the jury photos of the children's bodies.
The jury followed him closely.
Pruner showed magnified copies of Schenecker's journal entries before and after the shootings.
"I offed Beau," she wrote in one.
"I was planning on a Saturday massacre," she wrote in another, explaining how she bought a gun but had to wait three days for a background check.
Spradley told jurors that no one disputes that Schenecker killed her children, saying "this is not a whodunit."
She said what they need to do is consider Schenecker's state of mind when she pulled the trigger, that she was suffering from such severe depression and manic depression that she didn't understand what she was doing.
"Her mind is clouded. She didn't choose this illness - it chose her," Spradley said. "When she wasn't sick, she was a good mother."
She said that the family's frequent moves because of Parker Schenecker's military career exacerbated her illness.
All six mental health experts who testified during the trial said Schenecker was mentally ill, but the three called by prosecutors said she was legally sane when she shot her children.
Defense attorneys said Schenecker is so affected by bipolar disorder and depression that she doesn't know right from wrong. Under Florida law, the inability to tell right from wrong is one of the criteria for a not guilty by reason of insanity plea.
Testimony showed that Schenecker bought a .38-caliber handgun the weekend before the shooting, telling the gun store clerk she wanted it for home protection. But in her journal, she lamented the three-day wait for a background check, writing she had planned a weekend massacre. When she collected the gun, she bought more lethal hollow-point bullets.
A few days later on the way to soccer practice in the family minivan, she shot Beau twice, investigators found - once in the side of the head and once in his mouth.
She turned around, drove home and parked in the garage. Schenecker approached Calyx from behind and shot her once in the head and once in the mouth.
Schenecker wrote about the shootings in her journals, saying that she shot both teens in "their mouthy mouths."
She also put a sticky note on the calendar that said, "Beau is in the van on the way to practice. Calyx is in her bed, tried to make her comfortable."
In her journal, Schenecker addressed her husband, writing that he was lucky he wasn't in the house, prosecutors said. "I might have taken you out, too," she wrote.
Schenecker told detectives after her arrest, "This is the worst thing I've ever done."
Schenecker also wrote that she wanted to kill herself and wanted to be cremated with her children, their ashes mixed together. She mentioned that she was going to try to move her son's body into her bed and wanted to die next to him.
"Beau and I are going to heaven," she wrote. "Wish heaven for Calyx too."

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