ONLY ON ABC7NEWS.COM: Key witness in Hillsborough mansion murder, Olivier Adella, fears for his life as he prepares to testify against Tiffany Li and Kaveh Bayat

HILLSBOROUGH, Calif. (KGO) -- The key witness in the Hillsborough mansion murder case says he fears for his life after someone scratched the word "snitch" on his car. Meantime his family and friends are fighting back against new defense allegations that he is the real killer.

The murder of Keith Green in 2016 made international headlines. The San Mateo County District Attorney's Office charged Tiffany Li, her boyfriend Kaveh Bayat and Olivier Adella with the crime. Green is the father of Li's children.

RELATED: 15-page document reveals new details about Hillsborough mother's murder defense

Li was released from jail in 2017 when she posted $64-million bail in property and cash. Bayat remains in jail. While Adella cut a deal with prosecutors and agreed to testify against Li and Bayat. He pleaded no contest to accessory after the fact for disposing Green's body in Sonoma County. He was released in October after serving his time and is still expected to testify at the trial for Li and Bayat in August. Adella was Li and Bayat's bodyguard and trainer.

Adella and his wife say someone is trying to intimidate them by keying Adella's car before the August trial.

"There was some writing on it," Adella said.

"Snitch on it. It's pretty much intimidation if you ask me," he continued.

Adella says he is keeping his agreement with the San Mateo County District Attorney's Office to not speak to the media directly about the case but agreed to talk to us about the alleged witness intimidation as well as his struggle to find work after being released from jail in October.

"He's paid for what he's done and he's not denying his involvement to that degree," said Uta Bredenstein, Adella's wife.

Adella's attorney installed surveillance cameras in their home after their car was vandalized. Police have also stepped up patrols outside their home. Adella and his wife say they still feel uneasy.

"You start to look over your shoulder," said Bredenstein.

"Our son's daycare is right around the corner from where I work and the teachers have expressed concern. This is very public," she continued.

RELATED: Defense to ask for separate trials in Hillsborough murder case

This is the second allegation of witness tampering in the case. Last year an inmate in San Mateo County jail told ABC7 News that Bayat offered him one-point-five million dollars to say Adella had confessed to killing Green. Bayat's attorney James McNair Thompson denied that claim and says he is "suspicious" about this latest allegation of witness intimidation.

The San Mateo County District Attorney's office says the vandalism of Adella's car is under investigation. Also that it was not captured on surveillance video and there are no leads.

Adella says the notoriety of the case has made it difficult to find work.

"This case is very famous if you will," Adella said.

"They say 'Olivier,' we want to you work. We pay for the training. We would love to have you but we can't, we have to wait until this thing is closed," said Adella.

Adella is a professional mixed martial arts fighter. He says he was offered a fight in Las Vegas that could earn him as much as $250,000 but had to turn it down because he has to stay within 100 miles of Redwood City until after he testifies in the trial.

"Every time he applies for a job, the background search reveals results that will come up as him being involved in an open case," Bredenstein said.

Li's attorneys recently filed a 15-page trial brief stating that Adella was the real killer. Adella's friends and family say that makes no sense.

"It is a horrible tragedy for Keith Green," said Bredenstein.

"My husband did not even know him. I think he has seen him once, so why would he hurt someone that he doesn't know. There is no gain for him in any way," she continued.

In 2017, Adella told ABC7 News I-Team reporter Dan Noyes that he felt threatened when Li's boyfriend Kaveh Bayat showed up at his home with Green's dead body.

Bredenstein said, "Yeah, if you are backed against the wall and you know your wife and your newborn son is upstairs. I am not sure I am going to leave that up there. Who's to say. You just say no? And then what? He just shot his friend. The guy with the gun. What would you do? I have asked myself that question."

Adella's wife added that her husband had already turned down an offer from Li and Bayat to kill Green for 50-thousand dollars. A family friend told us that although Adella is a professional martial arts fighter, he leaves the the fighting in the ring.

"I believe that the media sees him as a sort of villain partially because of his size, profession and the color of his skin as well," said friend Oaday Awadalla.

Adella says he is having trouble finding work because of his association with the case. A judge wouldn't make an exception to the deal he made with prosecutors for him to travel to Las Vegas for a professional fight.

Adella said, "But the judge said a deal is a deal which is kind of funny because a deal is a deal when it comes to me but when it comes to the Chinese girl, a deal is not a deal. She can make a deal and then go back to change the deal so tell me there is no two (systems of) justice in this country."

Adella is also pushing back from the defense brief that quotes his ex-wife who calls him a "con artist." Adella says she is mentally unstable and is angry that he broke up with her.

Attorneys for Li and Bayat say that Adella is liar and can't be trusted. Li's attorneys will be back in court in Redwood City next month with a request that a judge allow the couple to be tried separately. They say Li will need to undergo more treatment for breast cancer in August when the trial is scheduled to start.