Is a former FSU student a battered child, mentally ill or a liar? A jury in her murder trial will be asked to decide.

TAMPA — The first expert will say Nicole Nachtman is a battered child, a young woman made to feel so helpless and afraid of her mother that death was seen as a way out.

The second expert will say Nachtman is mentally ill, that schizophrenia made her unaware of what she was doing or the consequences of her actions.

The third expert will say that Nachtman is a liar, who made up or exaggerated tales of abuse and mental illness after she shot her mother and stepfather in 2015 at their Carrollwood home.

Who can be believed? A jury will have to decide.

Nachtman, a former Florida State University student, goes on trial this week in a Tampa courtroom. She's accused of two counts of first-degree murder in the 2015 deaths of Myriam and Robert Dienes.

Her public defenders have set the stage for a two-pronged defense: that Nachtman was defending herself from her mother's wrath, and that she didn't know what she was doing because of mental illness.

If they succeed, she could spend time in a mental health facility. If convicted as charged, Nachtman, 25, will spend the rest of her life in prison.

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Background: Court documents: FSU student accused of murdering parents had difficult relationship with mother

Neighbors near a quiet Carrollwood cul-de-sac heard gunshots late on the night of Aug. 20, 2015. A 911 call summoned sheriff's deputies, who found a woman lying in the driveway. She was Myriam Dienes, 56. She had been shot three times.

The front door of Dienes' neighboring home swung open when deputies knocked. As they moved from room-to-room, they found a locked bedroom door. They pried it open and found a man lying beneath a blanket. He was Robert Dienes, 67. He had been shot once in the back of his neck.

Neighbors said they'd seen Nachtman near an open window about two hours before they heard the gunshots. When deputies phoned her, Nachtman, then 21, claimed that for the past day or two she'd been at Florida State University, where she was about to begin her sophomore year. But campus records would later show that Nachtman had not used her student identification card anytime during the prior week.

Her older half-brother, Joseph Carey, would later testify about a phone call he had with his sister a day after the shootings. At that point, he believed the deaths were a murder-suicide. As they spoke, Nachtman said she was going to miss him. He asked what she meant.

"You can call me a beast, but don't call me a monster," she said, according to court testimony.

He asked again what she meant.

"I shot them."

Nachtman cried and spoke of nightmares and "screaming in her head," and signs that said things like "you can do it," Carey testified.

She explained that the reason she shot her stepfather was because she had not obtained housing at FSU, according to a court document filed by prosecutors. She later learned that she had indeed obtained housing and if she'd gotten the news earlier she wouldn't have done it.

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She waited for her mother to return home from a work-related trip. But when she saw Myriam Dienes arrive, she became scared and tried to sneak away, according to the court document. Dienes saw her and angrily confronted her about why she wasn't in school. Nachtman then shot her, prosecutors said. She was later arrested at the FSU campus in Tallahassee.

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Previous coverage: Doctor testifies former FSU student turned murder suspect was abused

In January, Nachtman's public defenders asked a judge for permission to argue that she suffered from battered child syndrome.

They presented testimony from Kathleen Heide, a University of South Florida criminology professor and psychotherapist, who had conducted extensive evaluations of Nachtman in jail. Heide detailed a troubled relationship between mother and daughter.

A registered nurse and captain in the Navy Reserve, Myriam Dienes was known as strict, and sometimes struck others as mean.

She badgered her daughter about her weight, and at one point forced her to get liposuction, Heide said. She was verbally abusive, referring to Nachtman as a "worthless daughter" and an "overweight skank." At her high school graduation, Nachtman said her mother grabbed her arm and told her she was an embarrassment, Heide said. Nachtman also spoke of several incidents in which her mother hit or kicked her.

All of it, Heide said, made an emotionally stunted young woman who feared her mother's wrath.

Hillsborough Circuit Judge Christopher Sabella permitted Nachtman's defense to argue battered child syndrome in front of a jury but only as part of a self-defense claim to the killing of Myriam Dienes. The judge said he heard no evidence that Robert Dienes was abusive to Nachtman.

Weeks later, the defense gave notice they plan to argue Nachtman was insane. They listed a second expert witness, Charles Ewing, a lawyer, forensic psychologist and professor emeritus at the SUNY Buffalo Law School. He is expected to testify about symptoms of schizophrenia that Nachtman showed.

Assistant State Attorney John Terry asked that the state be permitted to have its own expert evaluate Nachtman.

The prosecutor tapped Emily Lazarou. She's a Tampa psychiatrist who has testified in scores of criminal trials.

She became a controversial figure months ago in the trial of John Jonchuck, who was found guilty of murder in the death of his 5-year-old daughter, Phoebe.

Defense attorneys in that case tried, unsuccessfully, to bar Lazarou from testifying, calling her methods biased and coercive. Jonchuck relied on an insanity defense. Lazarou was the only one of five expert witnesses in that case who said Jonchuck did not have a mental illness when he tossed his daughter from the Dick Misener Bridge.

Related: Hillsborough deputies: FSU student says 'screaming voices' led to murders of mother, stepfather

In the Nachtman case, Lazarou conducted a 14-hour evaluation, which occurred over three days.

In pretrial testimony July 11, Lazarou said she believed Nachtman lied or was evasive several times, according to a defense motion. She said Nachtman lied in describing her fear that her mother was going to kill her. She lied about the date on which she killed her stepfather, where she was standing when she fired the fatal shots, and why she killed him. She also lied, according to Lazarou, in her account to her brother about driving to Tallahassee and seeing posters that she interpreted as signs.

The doctor stopped short of diagnosing Nachtman with anti-social personality disorder, according to the defense motion, because Nachtman did not get in trouble as a child. The defense has asked that no such diagnosis be mentioned during testimony. They have also asked that Lazarou's testimony be limited.

Jury selection is set to begin Monday. The trial is expected to last two weeks.

Contact Dan Sullivan at dsullivan@tampabay.com. Follow @TimesDan.