Cold case investigator Paul Holes, who knows a thing or two about criminal deviants, calls the East Area Rapist “probably the worst serial predator in California history.”

The rapist terrorized women and couples from 1976 to 1985. He began on Sacramento’s east side with home-invasion sexual assaults in the dead of night. Thanks to a modern DNA database, we now know he then passed through the Bay Area, committing assaults in Contra Costa County and San Jose on his way to Southern California. There, after almost being caught, he began killing his victims.

The rapist hasn’t been heard from in 30 years. Holes, chief of forensics for the Contra Costa District Attorney’s Office, has been chasing his shadow for more than two decades, using every means at his disposal.

Recently a new out-of-the-box strategy was suggested to him. It involved taking the most tantalizing clue in the case — an approximately one-minute-long recording of the East Area Rapist’s voice — to volunteers from San Francisco’s LightHouse for the Blind and Visually Impaired, an agency that promotes self-reliance for people who have lost part or all of their sight.

The recording is of the rapist as he calls one of his victims after the fact. Once aware this was one of the rapist’s tactics, the Sacramento County Sheriff’s Department set up recorders on the phones of victims. In January 1978 they got a hit.

The quality of the recording isn’t great, even after being enhanced by modern technology. Holes says a breathy, hissing voice can be heard repeating, “I’m gonna kill you.” Later in the recording, other voices can be heard in the background. Holes believes the ambient noise could yield valuable clues if only it could be understood.

“I took it to the (Contra Costa) DAs and got very few responses,” Holes said. “Then (prosecutor) Melissa (Smith) said, ‘What about having a blind person listen to it?’ I said, ‘Oh, that’s awesome.'”

Smith’s premise was that blind and visually impaired people might hear something in the recording that investigators did not. Holes reached out to the staff of LightHouse.

“As blind people,” said Bryan Bashin, executive director and CEO of LightHouse, “many of us experience listening acutely. As we travel through space, we use sounds to give us positional cues and context — the richness of sounds that are often overlooked. Our senses are no keener. (But) we pay more attention to that information.”

Bashin was excited to be involved for two reasons. One: He remembers the East Side Rapist’s reign of terror.

“I lived in Sacramento years ago,” Bashin said. “He is among the most horrifying and audacious criminals I can remember.”

And two: “We like to be included.”

For Holes, it’s a unique chance to bring closure to victims who remain traumatized by this calculated, sinister criminal.

“They have a team, six people, then two lead guys who are going to listen,” Holes said of the volunteers. “Individually, each person will listen to the enhanced background voices, then we’ll get together as a group and discuss.”

The process is ongoing. Stay tuned.

If you have tips or information regarding the East Bay Rapist case, you can call Paul Holes at 925-957-8751.

Do you have a column topic for Gary? Contact him at 925-952-5053 or gpeterson@bayareanewsgroup.com. Follow him at Twitter.com/garyscribe.