Why an Insanity Plea Would Be ‘Very Hard’ for Nick Reiner: Experts (Exclusive)

Will Nick Reiner plead insanity after being charged with murder in connection with the deaths of his parents Rob and Michele Reiner? It remains unclear, but it’s a defense with a historically low success rate in court, according to legal experts. 

“To be found not guilty by reason of insanity, that is a very difficult legal hurdle to overcome in California,” Neama Rahmani of California’s West Coast Trial Lawyers, who is not connected to the Reiner family case, tells PEOPLE. “You have to prove, between disease or defect, the defendant does not know the nature and consequences of his actions. Essentially, you have to show that the defendant doesn’t know right from wrong.”

The When Harry Met Sally… filmmaker, 78, and his wife Michele, 70, were found dead in their Los Angeles home on Dec. 14. Their son Nick, 32, was then arrested and charged with two counts of first-degree murder; he is being held without bail at Twin Towers Correctional Facility, where, a police source told PEOPLE, he was put on suicide watch in solitary confinement. His charges carry a maximum sentence of life in prison without parole or the death penalty, if convicted.

“It is very hard,” says Rahmani, for most defendants to achieve a more lenient sentencing by pleading insanity in court. “Jurors almost always reject this defense. It only works a very small percentage of the time.”

Never miss a story — sign up for PEOPLE’s free daily newsletter to stay up-to-date on the best of what PEOPLE has to offer​​, from celebrity news to compelling human interest stories. 

That’s partly because of where an insanity plea falls amid legal proceedings, he continues, noting that first, prosecution must prove culpability and the defendant will “argue something” like self-defense. 

In the “second phase,” he continues, “the burden’s on the defense”: lawyers will typically attempt to argue a defendant is legally insane, thus reversing the earlier narrative. “Then they gotta turn around and say, ‘Oh, you know what? He actually did it, but he was insane.’ So jurors don’t like it, and it’s rarely, if ever, effective.”

In the case of Nick facing two counts of first-degree murder in connection with the deaths of his parents, with a special allegation of using a knife, surrounding circumstances could make a successful insanity plea “difficult,” New York criminal defense attorney and former prosecutor Randy Zelin tells PEOPLE. 

In a court of law, a “history of bad blood” could point to a possible motive, mitigating “not knowing that you’re engaged in criminal offense conduct,” says Zelin, who is also not affiliated with the Reiner case. 

Nick and Rob argued at Conan O’Brien’s Dec. 13 holiday party the night before the deaths, according to sources. Zelin offers his opinion that the manner of Rob and Michele’s death “suggests a conscious objective to kill” and his following actions, such as reportedly checking into The Pierside hotel in Santa Monica, Calif., “shows a level of awareness and reality.” 

“If you are coherent and capable enough to have an argument with your parents, that’s not legal insanity,” Rahmani similarly argues. 

However, Nick’s mental health and allegations of drug use “may play into the case,” adds Rahmani, following reports from The Los Angeles Times and KNBC that he was receiving medical treatment for schizophrenia at the time of the deaths.

“First-degree murder requires premeditation. So that’s plotting, planning, doing something intentionally. There is a possibility that the defense may use the schizophrenia to argue that there’s no premeditation. That would knock first degree murder down to second degree.”

Zelin argues that if Nick is convicted, his defense team could indeed use his “history of mental disease and addiction” to reduce sentencing to manslaughter, potentially “taking the death penalty off the table… Mental health experts here are equally if not more relevant than the lawyering.”

Nick made his first appearance in court on Dec. 17, wearing an anti-suicide smock and shackles. His attorney, Alan Jackson, declined to enter a plea for his client at that time. The Being Charlie screenwriter’s arraignment is scheduled to continue on Jan. 7.