All eyes are on Nick Reiner as he appears in a Los Angeles courtroom on Monday for the third time since facing charges for allegedly killing his well-known parents in their luxurious $20 million Brentwood home.

The arraignment is anticipated to be brief as he enters a plea, but according to a legal expert consulted by The Post, his public defender, Kimberly Greene, might seize this opportunity to begin establishing an insanity defense.

Here’s the latest on the death of Rob Reiner:

“Introducing a mental health defense early on is strategic,” explained lawyer Royal Oakes, “as delaying it might weaken the argument’s credibility later. People might question, ‘If his mental state is so severe, why wasn’t this raised sooner?’”

The defense could potentially argue that Reiner lacks the capacity to comprehend the legal proceedings. “They might invoke a competency challenge. Doing so could halt the case and initiate psychiatric evaluations,” Oakes elaborated.

Furthermore, the behavior Reiner exhibited at Conan O’Brien’s holiday gathering, just hours before the tragic event, could significantly influence the strength of an insanity plea, especially given the presence of A-list celebrities who witnessed it.

Party attendees recalled a heated argument between Reiner and his parents, noting that he was also disrupting conversations during the celebration.

“Did Reiner, hours before the murders, seem obnoxious but cogent, or did he seem disconnected from reality? That’s the essence of the insanity test in California.” said Oakes.

But Greene has no obligation to raise the issue at the arraignment, which is mostly procedural and not where evidence is argued.

“The defense is absolutely free to plead not guilty now and keep its mental health strategy under wraps. There’s no requirement that they tip their hand at this early stage,” the attorney said.

So far, Reiner’s plea has been postponed twice. The first was when hotshot lawyer Alan Jackson entered the case and wanted more time to talk with his client.

Jackson dropped out of the case in court seven days later, that move further derailed a plea and put Greene in the driver’s seat as head attorney on the case.

The December 14 murders of Rob and Michelle Reiner shocked Hollywood to its core. Nick Reiner was arrested the day after the bloody bodies were discovered.

He’s been locked up in LA’s county jail with no bail ever since his arrest.

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