This is the fourth in a five-part series about the murder of Mary Elaine Costa, the oldest cold case homicide ever to be solved in Riverside County. The following story is based on a review of more than 1,000 pages of county court transcripts, court exhibits, police interview transcripts, archived news articles and several interviews. To explore the whole series, check out The Coldest Case, a Desert Sun true crime story.

Need to catch up? Get started with The Coldest Case, Part One.

November, 2010 – Sitting in his home in Portland, Oregon, Jimmy Stellflug picked up the phone and called the cops. Thirty-eight years ago, back when he was just a boy, his mother had been murdered. If the cops weren’t going to catch the killer, he thought, they could at least hand over her damn ring.

Stellflug, 45, had made this call before, but never with any success.

Normally, he would be bounced back and forth by police dispatchers, operators and secretaries. He would wait on hold for a few minutes then leave a voicemail for somebody who would never call him back.

This time, things were different.

Someone transferred Stellflug’s call to the new Cold Case Unit, which the Riverside County Sheriff’s Department had created two years prior to focus on old murder mysteries.

A police lieutenant picked up the phone. Stellflug swore he could hear genuine interest in the cop’s voice. Stellflug started talking, reciting the story that had haunted him for most of his life.

His mother was Mary Elaine Costa. She had been found dead on a road north of Palm Springs on March 12, 1972. Someone had taken her money but left a Marine Corps ring on her finger. Stellflug didn’t know where the ring had come from, but he was hopeful the police would let him have it.

The ring would be a memento of a mother he barely knew.

“If you aren’t going to do anything about my mother’s case, I’d like at least like that ring,” Stellflug said.

“I’ll look into it,” promised Lt. Scott Brown. And so the lieutenant looked.

He found a lot more than just a ring.

At the Cold Case Unit office, the Costa murder file was buried in a stack of more than 1,700 unsolved cases that the detectives still needed to review. There was the mystery of a Palm Desert businessman who was sniped in his living room as he watched the moon landing in 1969. There was the case of a unidentified woman – shot, burned, her hands cut off – found at the Cactus City rest stop in 1977. There was a man with a weight around his neck drowned in the All-American Canal in 1975, a well-dressed woman thrown in a mountain ravine in 1980 and a body found in a shallow grave in Rancho Mirage in 1991.

Most of these cases had few clues and little hope. Most had gone cold for a good reason – the police had nothing left to work with.

But in the Costa file, the detectives found a surprise.

Back in 1976, two detectives, Ronald Dye and Terry Burdo, had interviewed an eyewitness, Diane Walker, and zeroed in on a suspect, Michael Jerome Hayes. The detectives were closing in on an arrest, but for some reason, their case had been shelved.

Now the Cold Case Unit had all their notes, reports and contacts. It was time for a new generation of investigators to get to work.

Two detectives, Brett Seckinger and Eddie Vargas, began by combing through witness statements and microfilm, studying everything that had been said or published about the case back in the '70s. They pulled Costa’s flower-print dress out of storage and sent it to a Texas lab for DNA testing. They found Walker in Kansas. She stood by the interview she had given in 1976.

Eventually, the Cold Case Unit reached the point where Detective Dye got stuck. It was time to talk to Hayes, who was now living in Fort Lauderdale with a new wife – at least his fifth – running a bar and raising birds for sale at pet shows.

This time, the bosses paid for a flight.

Seckinger and Vargas flew to Florida with one of Riverside County's top homicide prosecutors, Mike Hestrin, a future district attorney. Hestrin, the son of a Palm Springs cop, had grown up not far from the crime scene. He was just an infant when Costa was killed.

"We had an address for (Hayes,) but we weren't sure if it was good or not," Hestrin said in an interview, describing the trip to Florida. "So we went out there real early in the morning to check it out."

"And there he was, sitting on the front porch, drinking coffee."

Seckinger and Vargas asked Hayes if he would come down to the police station for a chat. He agreed, so the two detectives took Hayes into a cramped interview room, where he sat before them with his hands folded in his lap. Hestrin waited outside, watching the interview on a closed-circuit television, as Seckinger introduced himself in a chummy tone.

“We are actually from California,” Seckinger said. “But we network with other agencies, and when the name of a person of interest comes up, we get an alert on our end. And your name came up.”

The interview started friendly like that, with neither detective revealing that Hayes was a suspect. Seckinger pointed out that “Michael Hayes” was a “pretty common name,” so he wasn’t even sure he was talking to the right guy.

But the detective kept asking increasingly specific questions.

Did Hayes ever live in California?

Did he ever go to Palm Springs?

Did he ever work at the Biltmore Hotel?

Did he ever drive a yellow Volkswagen?

Hayes tried to be evasive, but he wasn’t very good at it. At first he didn’t remember living in Palm Springs or Indio, and then he said he did. Hayes said he wasn’t married when he lived in California, then abruptly remembered that he was. His ex-wife’s name was Diane, he said, and he was 17 when they married. He was actually 25.

Eventually, the detectives became exhausted with Hayes’ forgetfulness.

Seckinger stopped pretending this was a friendly chat.

“I’m not dealing with some economic crime,” the detective said. “I’m not dealing with a box full of checks and bank statements. I’m dealing with a homicide, which never goes away.”

Alarmed, Hayes buttoned up. Seckinger leaned on him harder, but Hayes said less and less. His cooperative tone gave way to terse, unhelpful answers.

He didn’t know anything about a murder, he said. He said he couldn’t explain why his ex-wife would implicate him in anything.

"Does she hate you that much?" Seckinger asked.

"I didn't believe so," Hayes said.

Seckinger dropped photos of Costa’s decomposing body on the table.

“I think it was an accident,” the detective said, baiting a hook.

Hayes didn’t bite.

“I didn’t do that,” he said. “I didn’t do that.”

Eventually, after more than an hour of questioning, the detectives decided to take a bathroom break. They stepped out of the interview room, leaving Hayes alone with his thoughts and the empty beige walls of the interview room.

Hayes grabbed his cell phone and dialed his wife.

“Beverly, get me some help,” he said. “They are saying I had something to do with a murder.”

Published on July 21, 2017

PART FIVE: For 40 years, he got away with murder. Then his ex-wives started talking.

Investigative reporter Brett Kelman can be reached at 760 778 4642 or by email at brett.kelman@desertsun.com. You can follow him on Twitter @tdsBrettKelman.