In a conversation surreptitiously recorded by her Ronkonkoma neighbor, a schizophrenic woman said her drug-addicted daughter could have been just as involved in the death of her infant grandson as the daughter’s boyfriend, who was convicted of manslaughter last year.

Parts of the recording, made March 14, were played Wednesday at a hearing to determine if the conviction of the boyfriend, Christopher Foster, 32, should be reversed. Defense attorney David Besso argued it should be because the child’s grandmother, Barbara Hertzler, told her neighbor earlier this year that she saw her daughter, Clarissa Hertzler, squeezing her baby’s head the morning of Oct. 11, 2011, when he died.

Foster was convicted last year of killing his son, 42-day-old Jonathan Hertzler, who died from multiple skull fractures. State Supreme Court Justice William Condon will decide later whether to reverse that conviction.

In the conversation with her neighbor, Carol Stalhut, Barbara Hertzler described a chaotic household. She said she was afraid of her daughter, who was on methadone for her opiate addiction, but was also stealing the anti-anxiety medication Xanax from her mother and using large amounts of cocaine, sometimes with friends she met at a club where she went pole dancing.

An autopsy found cocaine in the baby’s bloodstream.

“I think they gave that baby drugs,” Barbara Hertzler said, referring to Foster and her daughter, according to Stalhut. Clarissa Hertzler was not charged in her baby’s death.

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Assistant District Attorney Laura Newcombe tried to question the credibility of both Barbara Hertzler and Stalhut. Stalhut told Newcombe she was unaware that Hertzler had been committed twice to psychiatric wards or that in a recent hallucination, she saw Jesus Christ sitting on her couch.

Stalhut testified that her own bipolar syndrome has been under control for five to 10 years, but she told Condon during her testimony, “This is very nerve-racking.”

At times she had difficulty following along with a transcript of the recording she made of Hertzler. “Tell me where you are, babe,” Stalhut said to Newcombe as she flipped through the pages.

Stalhut insisted that when Hertzler described what she saw her daughter do to her baby, she was lucid. On the recording, Hertzler said she still believes Foster killed the boy but also thinks her daughter could have been involved. Stalhut urged her friend to speak up.

Barbara Hertzler, who is again committed to a psychiatric ward, was available to testify Wednesday and waited outside the courtroom. Neither side called her as a witness.

Besso said Stalhut’s testimony, the recording and other evidence was enough for Foster’s conviction to be reversed.

On the recording, Hertzler told Stalhut she was still afraid of her daughter.

“I’m having them locks changed before she comes home,” Hertzler said on the recording.

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“Very good idea,” Stalhut replied.