Former professional wrestler Jimmy “Superfly” Snuka suffered so many blows to the head during his long career that he now suffers dementia and is mentally incompetent to stand trial in the death of his girlfriend more than three decades ago, a psychologist testified on Friday.

Snuka’s severe mental impairment also stems from a history of abusing alcohol and cocaine, Dr Frank Dattilio said at the wrestling star’s competency hearing.

Snuka was charged with murder and involuntary manslaughter in 2015 in the 1983 death of 23-year-old Nancy Argentino, from New York. Snuka’s lawyer asserts he doesn’t understand the charges or even know he was arrested.

Lehigh county judge Kelly Banach, after hearing from prosecution and defense experts, will decide if Snuka is competent to stand trial.

Snuka, who was in the courtroom for Friday’s hearing in Allentown, Pennsylvania, has pleaded not guilty and is free on bail. His attorney, Robert Kirwan II, has called Argentino’s death an “unfortunate accident”.

Dattilio, testifying for the defense on Friday, said he had a “hell of a time” trying to get even basic background information from Snuka. The psychologist said Snuka could not assist in his own defense and quoted one of Snuka’s doctors as saying he’s a “shell of a man”.

“This is permanent damage, and he’s not likely to be restored to competence,” Dattilio said.

He recounted an infamous televised scene from 1984 in which another wrestler, Roddy Piper, broke a coconut over Snuka’s head. He said one side of the coconut had been shaved down so that it would easily break, but Piper inadvertently used the hard side on Snuka’s skull.

The hearing was adjourned until Wednesday, when a prosecution expert will testify.

Prosecutors assert Snuka is well enough to stand trial. During cross-examination on Friday, they played a video that showed him in the ring as recently as 2015 – even doing his trademark move, the Superfly splash, albeit from the second turnbuckle instead of the top.

Another video showed him giving an interview recently in which he appeared lucid and in character.

The wrestler had been at a World Wrestling Federation taping at the Allentown Fairgrounds, and he told police shortly after Argentino’s death that he had returned to their Whitehall Township hotel room to find her unresponsive in bed. She was pronounced dead at a hospital several hours later.

An autopsy determined she died of traumatic brain injuries and had more than three dozen cuts and bruises, and it concluded her injuries were consistent with being hit with a stationary object. But the case went cold, and Snuka continued his high-profile pro wrestling career.

After a 2013 story by the Morning Call newspaper raised questions about the case, Argentino’s sisters approached Lehigh county district attorney Jim Martin, who reopened the investigation.

A grand jury report said Snuka, a Fiji native who lives in Waterford Township, New Jersey, had provided more than half a dozen shifting accounts of Argentino’s injuries, at first telling paramedics he hit her during an argument outside their hotel room and she struck her head on concrete, then saying to police she slipped and fell during a bathroom break on their way to the hotel.

The grand jury also said it heard evidence that Snuka beat Argentino four months before her death and repeatedly assaulted his wife, Sharon Snuka, in the fall of 1993. Snuka has long maintained his innocence.

Snuka was known for diving from the ropes in a career that spanned four decades. He was admitted into the World Wrestling Entertainment Hall of Fame in 1996, according to the organization’s website.