NEW YORK -- The forensic psychiatrist who Manhattan prosecutors sought to have barred from testifying at Daniel Penny's subway chokehold trial revealed on the witness stand Tuesday that Jordan Neely had been hospitalized more than a dozen times for psychotic episodes and abusing synthetic marijuana before his death on a Manhattan train.

The mental health breakdowns included delusions that the rapper Tupac Shakur was using him to "change the world" and that he heard the "devil's voice," said Dr. Alexander "Sasha" Bardey, a defense expert who reviewed thousands of pages of Neely's medical records going back to 2015.

Penny, a 26-year-old Marine veteran and architecture student, is fighting charges of manslaughter and criminally negligent homicide in connection with 30-year-old Neely's death in May of last year.

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Bardey, a professor at NYU and the New York Medical School and an expert witness for the defense, previously worked at Rikers Island, the same jail where Neely screamed about returning to before Penny put him in a chokehold when he started making death threats on a Manhattan subway car.

Prosecutors unsuccessfully tried to have him blocked from testifying and to have evidence of Neely's mental illness and drug abuse withheld from the jury.

Neely had a documented history of paranoid schizophrenia, Bardey testified, after reviewing thousands of pages of the man's medical records.

The disorder impacts less than 1% of the population and can lead to hallucinations, delusions and false ideas that are impossible for the afflicted person to shake, Bardey said. He testified that he's worked with hundreds of schizophrenia patients and found Neely's case to be among the worst.

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"His symptoms ... I would classify as severe," he testified. "He describes paranoid fears that people want to hurt him, grandiose delusions that people are jealous of him, said that Tupac instructed him to change the world, and that's what he was doing."

He said Neely shared his Tupac claim with hospital staff on at least two occasions. In one instance, "when asked to elaborate, he rambled about people changing their hair color and giving out free food."

The medical records that Bardey reviewed also revealed that Neely heard "the devil's voice."

He said Neely was illogical and disorganized and described his behavior as "aggressive [and] bizarre."

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Schizophrenia patients can't tell the difference between their hallucinations and reality, Bardey said. Delusions can be triggered by a number of factors, including drugs, drinks and even food.

People with paranoid schizophrenia can be more dangerous to themselves and others, he added, and they don't think clearly or respond to reasoning.

The use of synthetic marijuana, which a toxicology report found in Neely's system after his death, can have a severe effect, he testified, especially when they aren't taking their antipsychotic medication.

Bardey's testimony followed that of Penny's mother, two Marines who he served with overseas, and other character witnesses who described him as a man of integrity and empathy.

The servicemen revealed in court that Penny received a Humanitarian Service Medal for his work in the aftermath of Hurricane Florence in 2018.

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Gina Flaim-Penny, his mother, said Penny returned to his home state after an honorable discharge and studied architecture at New York City Tech in Brooklyn, working nights at a restaurant there and also teaching swimming lessons at a gym in Manhattan.

Neely, a homeless man who has been described as a former Michael Jackson impersonator, barged onto the train, threw his jacket on the ground and started shouting death threats, telling straphangers he did not care if he went to prison for life, according to witness testimony.

When they let go, Neely still had a pulse, but the forensic pathologist who conducted his autopsy, Dr. Cynthia Harris, testified that it is normal for someone's heart to keep beating for some time even if they have been choked to death. In her autopsy, she ruled that Neely's death was due to asphyxiation from the chokehold.

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Penny faces up to 15 years in prison if convicted on the top charge of manslaughter. He also faces a lesser charge of criminally negligent homicide.