LOS ANGELES >> New York real estate heir Robert Durst testified today that he lied for decades about sending police a note directing them to the dead body of his best friend because he feared it would implicate him in the killing.

It was so hard to fathom that Susan Berman’s killer was not the same person who sent police a note directing them to her “cadaver” that Durst even questioned the plausibility of that explanation.

“I have difficulty believing it myself,” he testified in his defense in Los Angeles County Superior Court. “It’s very difficult to believe, to accept, that I wrote the letter and did not kill Susan Berman.”

Durst, 78, has denied killing Berman during four days of testimony at his murder trial.

Durst, the estranged eccentric heir to a commercial real estate fortune in New York, is only charged with Berman’s December 2000 killing. But Los Angeles prosecutors have introduced evidence of a presumed killing he is suspected of committing in New York and one he admitted to in Texas to prove the Berman case.

Prosecutors say Durst killed Berman to silence her before she could tell New York investigators how she provided a false alibi for him when his first wife vanished in 1982. They say he murdered a Galveston, Texas, neighbor in 2001 when the man discovered his identity while he was in hiding after New York police reopened the investigation into his wife’s disappearance.

Durst has denied killing Kathie Durst and has never been charged with a crime connected with her disappearance. Her body has never been found, but she has been legally declared dead. He was acquitted of murder in the killing of Morris Black in 2001 after testifying he shot the man in self-defense during a struggle for a gun.

Durst, who skipped bail in the Galveston case before eventually being arrested for shoplifting a sandwich in Pennsylvania, testified that he considered committing suicide while he was on the lam.

“I was going to shoot myself because I couldn’t imagine being a fugitive,” he said.

Durst, who is frail and suffering from a series of health problems, spoke in a soft, raspy voice as he denied killing Berman, his longtime pal who served as a spokeswoman when his wife went missing.

He showed no emotion describing how he found Berman lifeless when he showed up at her Los Angeles house during a planned visit a few days before Christmas.

Durst said there were cars parked out front and he found a note taped to her front door telling him she had gone for a walk. No one answered when he repeatedly rang the doorbell and knocked, so he let himself in with a key she gave him.

Her dogs barked incessantly, which was common, and he found a rear door to the house open and went into the backyard searching for her.

When he returned to the house, the front door was open and the note was gone. He said he may have left the door open after entering.

He found Berman lying on her back on a bedroom floor.

“I did a double take when I saw Susan,” he said. “I put my hand over her face … to see if she was breathing, to see if I felt breath. It felt cold. Then I grabbed her by her arms … her head just hung down. I could see that her hair was in some kind of liquid.”

He initially thought she was injured from a fall, but eventually concluded someone killed her.

He tried calling 911 from her home, but the battery in her cordless phone was dead. He decided to leave the house after hearing neighbors walking by and thinking he would be suspected if he was found inside with the body.

Durst said he stopped at a pay phone near Sunset Boulevard and dialed 911. He didn’t want to provide his name to the dispatcher and considered providing a phony name. But he concluded his distinct voice would eventually be recognized on the recording, so he hung up.

“I decided that instead of calling 911 I would send police a letter telling them that Susan was dead in her house,” Durst said.

He mailed a note to police that simply said, “CADAVER” and included Berman’s address. The envelope misspelled Beverly Hills as “Beverley.”

Durst said he didn’t remember the details of writing the note because he was in a fog after taking an opioid pain-reliever the night before for a migraine headache.

Durst had always denied writing the note — to police and documentary filmmakers who confronted him with a letter he once sent Berman with nearly identical handwriting and the same misspelling of Beverly.

After the judge ruled that prosecutors could present evidence showing he wrote the note, his lawyers conceded before trial that Durst penned it. His testimony was the first time he’s publicly described finding Berman and writing the note.

Durst denied killing Berman and said he had no motive to kill her. He denied that Berman, who was was in financial trouble and had been supported by him over the years, had been blackmailing him.

“Someone must have had a reason, a motive, whatever, to kill Susan Berman,” he said. “I had no reason to kill Susan Berman.”

When Durst wraps up his questioning from his lawyer, he is expected to come under withering cross-examination from Deputy District Attorney John Lewin.

During arguments today over evidence, Lewin said Durst had repeatedly lied on the witness stand.

“He has perjured himself probably 100 times and that’s not hyperbole,” Lewin said. “He’s testified inconsistently with other statements he’s given under oath.”