The side of a freeway ramp in Moorpark will be dug up Monday by dozens of police officers and FBI agents in an effort to recover the remains of a 15-year-old San Fernando Valley boy, murdered 40 years ago and buried there by California's worst child serial killer.

Roger Dale Madison was last seen leaving his home in Arleta on his motorcycle on Dec. 14, 1968. Several months later, Mack Ray Edwards confessed to Los Angeles police that he had kidnapped, abused, killed and then buried the boy along a freeway north of Thousand Oaks.

A series of hunches and coincidences, clues and science have led officers to a place near the southbound ramps of Highway 23 at Tierra Rejada Road where four police cadaver dogs have indicated that a body was buried.

"We've had four dogs independently indicate that a body's there," said Los Angeles Police Department Detective Vivian Flores. A particle detector that sniffs out decaying human bones "went off like a Geiger counter in the same place; it clicked so fast you wouldn't believe it," she said.

A ground-penetrating radar has detected "an anomaly, or a void" in dirt that was scraped away from a hill and dumped to build the onramp and off-ramp in 1968-69, she said.

A team of 30 LAPD officers, assisted by the four police dogs, 30 Ventura County reserve deputies and a team of 44 FBI agents, will converge on the ramps to "work with hand shovels, trowels and toothbrushes," the detective said.

The work will take five to 10 days, and it will be painstakingly thorough, Flores said.

Tents will be put up, sifting stations set up, a command post established and a news media corral set up for the reporters and photographers expected. Ramps may be closed occasionally as well, Flores said.

"We certainly appreciate the patience of the motorists," Flores said.

The abducted boy's brother and three sisters all live outside California and have supplied DNA samples for comparison. They are anxiously awaiting results, she added.

"We have gone to all of these police officers and basically asked them to donate a day or two of their time," Flores said. "They all instantly agreed, and the family told me they appreciate that so much.

"The mother and father have passed away, and one of the sisters told me the family hasn't placed the ashes anywhere permanently. Now that they might get Roger's remains, they hope to place all three in one place. It means closure for them."

Working off tips

The spreading news of the multiple killings and the Moorpark site may also mean some additional cases for investigators to work on.

Flores said people have come forward with old information about the confessed killer, and one of those calls came from a newspaper reader in response to a Sept. 18 news report in The Star about the Moorpark investigation site. The reader gave detectives leads about another child from the late 1960s who may have been killed, Flores said.

The cold-case detective has been working on the case of the missing Madison boy since clues were uncovered by Pasadena book author Weston DeWalt, who found records that Edwards had been employed by the company that built the freeway in 1968.

DeWalt first began investigating Edwards three years ago, when he recognized a police sketch of the man who may have kidnapped and killed a boy north of Altadena in 1957.

DeWalt realized the suspect looked like a picture of Edwards from a 1970 newspaper account of his trial.

Working off tips from DeWalt, Flores reopened the Madison case and realized that same stretch of freeway was being widened at the time of the boy's disappearance, she said. She went to a California Department of Transportation construction meeting and asked if anyone there had been present in 1968 when the original earth-moving project for the freeway was under way.

"One guy in the back of the room says he was there, but incredibly, he knew a retired Caltrans engineer who is now up in Northern California who kept detailed construction logs for everything he had ever done. This man had a Caltrans calendar that said Mack was working on the Tierra Rejada offramp on Dec. 14, 1968."

That was the day Roger Madison disappeared, and several months after it, Edwards walked into an LAPD station to confess that he had just kidnapped a teen girl and had tied her up in an orange grove.

The terrified girl was rescued, and Edwards tried to clear his conscience by confessing to a string of at least 18 slayings of children dating back to at least 1953.

He's under the freeway'

Edwards was sentenced to death row at San Quentin for his admitted killings of Madison and two other children, and he confessed to police detectives that he was responsible for other deaths as well. Some of his confessions reportedly were recorded by a police stoolie in a jail cell who was overhearing Edwards boasting about his crimes to cellmate Charles Manson Jr., DeWalt said.

DeWalt has been researching the cases for three years and is writing a book about them.

Flores said LAPD archivists could not find the "murder book" containing police records from Madison's 1968 disappearance but lucked out when they found a transcript of Edwards' confession in the records for a different slain child, Donald Alan Todd.

In that transcript, Edwards confessed he made contact with the Madison boy, slashed his neck, and tossed the child's corpse into a hole and covered it with rocks on the construction site north of Thousand Oaks. The interchange is now in Moorpark, which in 1968 was a small settlement over the next hill.

At the time of the confession, Edwards took LAPD detectives to the shoulder of the Santa Ana Freeway in Downey, where they discovered the body of Stella Darlene Nolan, whom Edwards killed and buried there in 1953.

"But he told the detectives, You'll never find Roger, he's under the concrete, his family is not rich and he's under the freeway,'" Flores said.

In 1971, Edwards committed suicide by hanging himself with a television set cord, and the investigation petered out.