After 40 years of silence, a former California Highway Patrol officer says he knows the identity of the Zodiac killer.

In his book, "The Zodiac Killer Cover-up," Lyndon Lafferty, 79, says the serial killer is a 91-year-old recovering alcoholic who is living in Fairfield, Calif., outside of Napa Valley. He chooses not to ID the man.

Lafferty is hardly the first to claim he knows who the killer is. At least two other books and two TV programs have profiled other alleged suspects. But none of the claims have ever been substantiated.

Lafferty says the killer's rage was driven by an adulterous wife. According to him, the case was covered up by law enforcement agencies and an unnamed judge who Lafferty says was having an affair with the killer's wife.

[ More photos: Images from the Zodiac killer investigations ]

"The police departments in general were acting under the authority of the Solano County Sheriff, so they were instructed you do not investigate this man until you have permission from the judge," Lafferty told ABC News. "I am the only person who can testify under oath that these things were absolutely true. My satisfaction is telling my story as it happened."

The Zodiac killer is named for the symbols used as a signature in coded messages to police. He claimed to kill 37 around the San Francisco Bay Area in the late 1960s and early 1970s, although police linked him to only five killings.

Lafferty told CBS San Francisco he met the Zodiac killer at a rest stop while working as a CHP officer in 1970.

"(It was) like I was looking into the eyes of death," he says.

Lafferty spent the next 30 years tailing the suspect and gathering evidence with six other investigators. In 2002, he began compiling his notes for the book.

"I've gone through 40 years of frustration," says Lafferty.