Ron Jeremy will be declared incompetent to stand trial.
The 69-year-old adult film star - whose full name is Ronald Jeremy Hyatt - is facing over 30 counts of rape and sexual assault but is said to be suffering from "severe dementia" and will likely be placed in a state-run hospital when he is declared unfit for trial on 17 January.
In an email obtained by the Los Angeles Times newspaper, LA County Deputy District Attorney Paul Thompson said mental health experts had been enlisted by both the 'Terror Firma' actor's legal team and prosecutors, who determined his condition and found no evidence he was faking.
He wrote: "As a result of the agreement of the experts, the defendant will be declared incompetent to stand trial ... his prognosis for improvement is not good.
"If he does not improve, we will not be able to try him for his crimes.
"Because criminal proceedings are suspended as long as he is incompetent, we also cannot get a guilty plea from him or discuss other measures to get justice for the victims in this case."
As well as examining medical documents, experts reached their decision based on interviews with the accused, his family and LA County sheriff's deputies, who had interacted him during his incarceration, with some suspecting he suffered from dementia before his arrest in 2020.
One of Jeremy's accusers, Lianne Young, told the outlet she was "kind of numb" after hearing the decision.
She said: "It's going to come down to public opinion now, and public opinion has looked at Ron like a god.
"It could be an indication to other predators or viewers of pornography that they can get away with such crimes."
Jeremy faces a dozen counts of forcible rape, seven counts of forcible oral copulation, six counts of sexual battery by restraint, four counts of sexual penetration by a foreign object and two counts of sexual penetration of an unconscious or asleep person.
The actor also faces one count of committing a lewd act on a minor, stemming from an accusation he sexually assaulted a 15-year-old girl at a party in Santa Clarita, California, in June 2004.
Los Angeles District Attorney George Gascón previously said in a statement: "Far too often, survivors of sexual assault suffer in isolation. We must ensure that survivors have all options available to help with recovery, including trauma-informed services for healing and support to report such crimes."
Ron has entered a plea of not guilty to all charges.