Nick Reiner has been formally charged with two counts of first degree murder, after his parents, Rob and Michele Reiner, were found dead in their home over the weekend.
The suspect had been expected to appear in court on Tuesday morning, but did not attend after his lawyer said he had not been "medically cleared".
He is currently undergoing the medical process, and will later be read the charges at the arraignment and will enter a plea of guilty or not guilty in court.
Due to the delay, it was confirmed: "If there is evidence of mental illness, it will appear in court, in whatever details the defence seeks to present."
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It was deemed too early to say whether there was any evidence of mental illness.
Prosecutor Nathan Hochman said that the crime is believed to have been committed with a knife.
The charges that he is facing carry a maximum sentence of life imprisonment or the death penalty.
Mr Hochman confirmed: "No decision has yet been made with respect to death penalty."
Nick Reiner has been formally charges with two counts of first degree murder, after his parents, Rob and Michele Reiner, were found dead in their home over the weekend
| GETTYPolice said that the suspect was found in a Los Angeles park, and was arrested without incident through "good, solid police work" by detectives and the US Marshal Service.
Cases involving family members are "some of most challenging and heart-wrenching cases", according to Mr Hochman, who described Mr Reiner as "an iconic force" in the entertainment industry and Michele as an "equally iconic photographer and producer."
"Their loss is beyond tragic," he said. "We will commit ourselves to bringing their murderer to justice."
Police also warned against "rank speculation, rumour or hearsay" on the case.
Rob Reiner and his wife Michele Singer were found dead in their home on Sunday | GETTYThe 78-year-old filmmaker and his 68-year-old spouse were found with knife wounds at their mansion on Chadbourne Avenue on Sunday afternoon, according to law enforcement sources.
Emergency services received a call requesting medical assistance shortly after 3:30pm local time. Upon arrival, firefighters contacted police to investigate.
Officials confirmed on Tuesday that they cannot confirm the time of death, as they away the coroner's report.
A family spokesman said: "It is with profound sorrow that we announce the tragic passing of Michele and Rob Reiner.
"We are heartbroken by this sudden loss, and we ask for privacy during this unbelievably difficult time."
Mr Reiner carved out an extraordinary career spanning seven decades in the entertainment industry, following his father Carl Reiner into show business.
He first achieved widespread recognition portraying Michael "Meathead" Stivic, the liberal son-in-law to Carroll O'Connor's conservative Archie Bunker in the groundbreaking sitcom All in the Family.
The role earned him two Emmy Awards and five Golden Globe nominations during his eight-year tenure on the programme.
His transition to directing proved equally successful, with the influential 1984 mockumentary This Is Spinal Tap one of his most notable projects.
Mr Reiner's CV also boasted work on Stand By Me, The Princess Bride, When Harry Met Sally, Misery and A Few Good Men.
He met his wife, Michele, while making When Harry Met Sally in 1989, and the couple married that same year.
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