Nick Reiner, 32, has been indicted on upgraded murder charges including a “lying in wait” special circumstance that could bring the death penalty.
The indictment, filed July 20 and unsealed Wednesday, alleges the screenwriter ambushed his parents before stabbing them to death in their Brentwood home.
He pleaded not guilty in a Los Angeles courtroom on Wednesday.
The new charges accuse him of using a dangerous and deadly weapon, a knife.
The “lying in wait” allegation makes him eligible for life without parole or capital punishment under California law.
Los Angeles County District Attorney Nathan J. Hochman issued a statement after the unsealing.
“This was a profound betrayal by someone who was loved and trusted by the very people he is accused of killing,” Hochman said.
He continued, “The indictment unsealed today also adds a special circumstance allegation that the defendant committed the murders by means of lying in wait.”
Hochman added, “We hope that by having a grand jury return an indictment in this case it will bring us one step closer to a trial and achieving justice.”
The grand jury indictment allows prosecutors to bypass a preliminary hearing and proceed directly to trial.
Nick had previously pleaded not guilty in February to two counts of first-degree murder with special circumstances of multiple murders and deadly weapon use.
His public defender, Kimberly Greene, entered that plea on his behalf.
He has been held without bail since his December 14 arrest.
The case has been marked by delays and legal upheaval.
High-profile attorney Alan Jackson withdrew from representing Nick in January, citing “circumstances beyond our control, but more importantly, circumstances beyond Nick’s control.”
Jackson had previously stated, “Pursuant to the law in California, Nick Reiner is not guilty of murder.”
Nick was then assigned a public defender.
In June, he filed a petition seeking access to a trust fund established in his name, claiming he needed the money for legal fees and basic jail commissary items like socks and soap.
The petition stated, “Nick loved his parents, and he is devastated by their deaths.”
It also noted, “The facts about what did and did not happen to them are not at issue in this Trust litigation.”
Law enforcement sources have said Nick was being treated for schizophrenia before the killings.
He spent time on suicide watch at Twin Towers Correctional Facility and remains in a high-observation mental health unit.
In the viral moment that started the case, Rob Reiner, 78, and Michele Singer Reiner, 70, were found dead in their Brentwood home on the afternoon of December 14.
They had been killed by multiple sharp force injuries.
Hours earlier, the couple had attended a holiday party at Conan O’Brien’s home.
Nick, who had been living on his parents’ property, allegedly got into an argument with his father at that party and was seen acting strangely.
He was arrested hours later in downtown Los Angeles.
His siblings, Jake and Romy Reiner, said in a statement, “Words cannot even begin to describe the unimaginable pain we are experiencing.”
They added, “The horrific and devastating loss of our parents, Rob and Michele Reiner, is something that no one should ever experience.”
The family later announced they were “grateful for the outpouring of love” and planned a future memorial service.
Autopsy results had remained incomplete for months, contributing to case delays.
At an April hearing, Deputy District Attorney Jonathan Chung said the preliminary hearing could not proceed because autopsies were still not finalized.
Nick sat mostly silent in a yellow prison jumpsuit during that brief appearance.
A judge had previously set his preliminary hearing for September 15.
The District Attorney’s office has not yet decided whether to actively seek the death penalty.
Hochman has said his office would examine all aggravating and mitigating circumstances, including mental health concerns raised by the family.
Nick’s next court appearance is scheduled for September in Los Angeles.