Last month his lawyer tried to convince a parole board that Sirhan Sirhan was a brainwashed hit man when he gunned down Sen. Robert F. Kennedy at the Ambassador Hotel in Los Angeles in 1968.

But handwritten notes purportedly from Sirhan, kept for 42 years by a Century City business executive, suggest that his behavior was calculated and controlled as he waited to shoot the presidential candidate in the hotel’s kitchen pantry area.

Michael McCowan was an investigator and the youngest member of Sirhan’s defense team in 1969 when the accused assassin wrote the narrative of his visit to a target practice range and his later election-night trip to the hotel trip on a legal notepad.

“He wrote it right in front of me,” said McCowan, now 78. Sirhan signed a second statement giving McCowan the rights to the documents, which next week will be sold by a Brentwood auction house.

In March, Sirhan appeared before a parole board for his 14th hearing since his conviction in May 1969.

The lawyer currently representing Sirhan suggested he was “manipulated” and “set up” and did not act alone when Kennedy was shot.

William Pepper, who could not be reached Wednesday for comment at his New York office, said Sirhan did not remember the shooting because he was “hypno-programmed” to kill Kennedy.

McCowan disagrees. “It never seemed to me to be a conspiracy. He wanted to be a martyr for the Palestinian cause,” he said of Sirhan.

“Sirhan’s not stupid. In his 10th-grade history book from his high school in Pasadena he’d underlined the assassination of President McKinley and on the next page of Archduke Ferdinand.”

Sirhan had then written words to the effect that there would be many more such assassinations, McCowan said. “I think he wanted to be a martyr. To me, he was the first terrorist,” he said.

Before volunteering for Sirhan’s defense team, McCowan had been a Los Angeles police officer and earned his law degree. He offered to help defense lawyers “because everybody’s entitled to a defense, to their day in court,” as he put it Wednesday.