CEDAR RAPIDS (AP) — He didn’t start out thinking he was going to solve a cold case murder that haunted Cedar Rapids for 38 years, but he always believed it would happen someday because the victim’s family deserved to know.

Matthew Denlinger was only 5 when Michelle Martinko, an 18-year-old high school senior, was attacked and stabbed to death Dec. 19, 1979, at the recently opened Westdale Mall. Her body was found the next day in her family’s Buick near J.C. Penney.

As he got older, he learned more about the case because his father, Harvey Denlinger, was a Cedar Rapids police detective at the time. The older Denlinger joined the department in 1970 and by 1979 had been promoted to a detective, now called investigator.

“We lived in Cedar Hills, only a couple miles from the mall,” said Matthew Denlinger, who, like his father, also became a Cedar Rapids police investigator. “That was our mall. We took pride in that mall. Lindale was for Eastsiders.”

Harvey Denlinger wasn’t assigned to the Martinko case, but he interviewed several Kennedy High School students, where Martinko attended school, and conducted other canvassing of the area as police searched for a suspect.

Anytime his parents would drop off a young Denlinger and his siblings at the mall, they wouldn’t necessarily mention the Martinko slaying but they would stress safety — “meet us here at this time, don’t go outside the mall, don’t wander around were you shouldn’t be.”

“The whole city was affected, for sure,” Denlinger, now 46, told The Gazette during an interview at the police department. “This young, vulnerable person was involved and to never get an answer — it feels like the danger isn’t out of town.”

Growing up, Denlinger had no plans to go into law enforcement. He set out to be a special-education teacher. His spent a lot of time caring for one of his seven siblings, his brother, Jamie, who had special needs and died in 2005. Denlinger finished his student teaching in Davenport, but after college wanted to try something different.

His father never talked him into or out of a law enforcement career, but was supportive when Denlinger became interested in following his dad’s footsteps.

“We are wired the same way … think the same way,” he said.

Harvey Denlinger was 44 at the time Martinko was killed. Coincidently, Denlinger was the same age when he helped solve the killing with the arrest of Jerry Burns, 66, of Manchester, on Dec. 19, 2018.

When Denlinger took over the cold case in 2015 from investigator Doug Larison, he followed Larison’s “master plan” of obtaining more DNA from possible suspects to compare with the profile that criminalists with the Iowa Division of Criminal Investigation has developed in 2005 from blood on the back of Martinko’s black dress that she was wearing the night she was killed.

Investigators before him believed the suspect had cut himself while stabbing Martinko. They knew she fought him by the many defensive wounds on her arms and hands. She was stabbed 29 times. The fatal blow was to the sternum, which penetrated her aorta. She bled to death, according to trial testimony last month.

The DNA evidence, which showed less than one out of 100 billion of unrelated individuals would have the same profile, was solid.

It was only a matter of time, Denlinger thought.

“I had plenty of hope but no expectation of how long it would take,” he said.

Going through the hundreds of boxes of information and reports in this case would be “overwhelming,” he said.

“That’s not how you start on a case that big,” he said. “You start by pouring yourself a cup of coffee and wheeling yourself over to Larison’s desk so he can tell you about the case and why it’s solvable.”

He also talked to J.D. Smith, a retired investigator who volunteers one day a week to work cold cases. After hearing all their experiences and stories, Denlinger recalled, “I’m all in.”

Of course, after working on the case for five years and going down many “rabbit holes” with theories and suspects, he ended up reading every report in the file — about 7,800 pages.

After eight months of working the Martinko investigation, Denlinger grew impatient. Authorities needed a new plan to narrow down possible suspects — not “swabbing everyone at random” for DNA samples.

In 2015, Denlinger bought his wife, Nicole, a DNA kit from Ancestry to explore her family roots. He remembered looking at the map of world where different areas were highlighted, showing where her ancestors lived.

“My wife suggested, ‘What if you could do this with your case?’ Denlinger said. “I was like, ‘exactly. Great idea.’”

He called officials at Ancestry to see if he could upload the suspect’s DNA profile into their system, but they told him that’s not what the service provides.

The company wouldn’t let law enforcement submit samples to compare with its clients. So the state crime lab suggested calling private labs.

Denlinger said a lab in Utah led him to Parabon NanoLabs, a Virginia company that helps law enforcement use DNA — a process called Snapshot — to predict what a suspect might look like based on the DNA profile, which could generate new leads.

It was an expensive process — $5,000 — so he had put together a presentation to his supervisors to sell them on the idea. Denlinger stressed they were working against the clock. It was 2016, and chances were the suspect was closer to death. Martinko’s parents had died in the 1990s, but her older sister, Janelle Stonebraker, and Stonebraker’s husband, John, deserved answers while they were still alive, he believed,

When the images generated from the DNA profile were shown to the public in 2017, police received hundreds of tips and leads. Authorities collected over 125 DNA samples. But still, none led to a murder suspect.

In 2018, Denlinger felt something else had to happen. He kept thinking about his wife’s Ancestry results, and wondered if building a family tree could help this case.

About that time, the “Golden State Killer” who had terrorized California in the 1970s and 1980s with at least 50 murders was finally arrested — with the help of genetic genealogy.

Soon after, Parabon NanoLabs called Denlinger to explain the process. The lab could upload the Martinko suspect DNA to GEDmatch, a public database, which might provide the suspect’s family trees.

“I knew we had something,” Denlinger said.

He received the report showing four family trees of great-grandparents. His task was to find living relatives, collect their DNA samples and find one that shared DNA with the suspect.

He wasn’t discouraged about the work ahead, but may have been “naive,” he said.

He and the Smith, the retired investigator, used several resources — county records, gravestones, newspaper clippings, birth and marriage announcements and obituaries — to find possible relatives on the family trees. They came up empty-handed on two branches, but found a hit on the third.

It was Brandy Jennings from Vancouver, a distant cousin, and she led to Janice Burns, who was likely a first cousin of the suspect.

In fall 2018, Denlinger interviewed Janice Burns, and she was “so nice and accommodating.” She provided him a DNA sample and even provided him with a family tree of her own.

Parabon took that sample and narrowed it to one of three brothers.

Denlinger and two officers started covertly collecting DNA samples from the three. A drinking straw was collected from one, a toothbrush from another’s trash and a drinking straw from Jerry Burns. This took about two weeks.

Denlinger collected the straw from Jerry Burns after watching him sip several sodas on Oct. 29, 2018, at the Pizza Ranch in Manchester.

“Sitting that close to him … there was a bit of tension in the air because you know there’s a 33.33 chance this is the suspect,” Denlinger said. “Of course, he didn’t know who we were. I was feeling excited thinking this might be it.”

Denlinger said he wanted to make sure everything was done “by the book — they weren’t violating anyone’s rights and doing justice to the case.”

He called the Stonebrakers and told them the suspect list was narrowed to three, but didn’t give them any names. He wanted to be cautious.

Denlinger also told his father they found the suspect and he was still alive and in this area.

But there still was more work to do. He and Smith had to conduct background checks on the brothers, which provided no obvious connections to Martinko or Westdale Mall. They exhausted everything — looking at cars and vehicle tags and jobs. He wanted to be prepared before the interviews.

Other investigators interviewed Burns’ two brothers at the same time Denlinger and Smith went to see Jerry Burns at his business. He was convinced the other brothers knew nothing about the murder.

Denlinger was equipped with a covert camera on his coffee cup when he and Smith went to talk with Burns. The possible suspect agreed to talk to them.

Denlinger said he wasn’t surprised by Burns’ calm demeanor. Everyone reacts differently in situations like this, he noted.

As the interview went on, Denlinger thought Burns’ behavior was “odd or strange” after he was told police found his DNA at the crime scene.

Denlinger was surprised when he asked Burns if he had “murdered someone” and Burns’ only response was “Test it” — meaning the buccal swab Denlinger had taken based on a search warrant.

Burns tried to change the subject. He brought up his cousin, who went missing Dec. 19, 2013. While saying he remembered Martinko’s slaying back when it happened, Burns brought up Jodi Huisentruit, a news anchor for KIMT-TV in Mason City who went missing in 1995 — a case Denlinger hadn’t mentioned.

“Honestly, I just think he was scrambling (for what to say) after 40 years,” Denlinger said. “He didn’t have a good answer. Any answers that he had prepared, he never had to use. If he had plans of what to say when police showed up, he had forgotten them.”

Burns was arrested at the end of the interview. After being read his Miranda rights, Burns continued to talk — mostly making more denials — to Denlinger in the ride to the police department.

“It was surreal at that point” sitting next to Burns in squad car, Denlinger said.

The investigator said he was “confident” Burns had killed Martinko, but “I always want to find out why.”

That is another sad part of this case for the family and friends of Martinko. Burns wouldn’t say why he killed the teen.

Denlinger didn’t have doubts police had the killer, but the unknowns of a murder trial made him nervous.

But early in the two week trial, he realized First Assistant Linn County Attorney Nick Maybanks and assistant Linn County Attorney Mike Harris put together a “rock solid” case.

“I knew it was in good hands,” he said.

Maybanks said nobody knew more about the case than Denlinger and that’s why he wanted Denlinger to sit with him and Harris at the prosecution’s table at trial — the first time Maybanks has asked an investigator to do sit with him.

Denlinger was “indispensable” in preparing the case for trial, Maybanks said. He was the source when it came to the investigative file.

“We also bonded early over the vibrant memories we both had of Westdale, the impact the homicide had on the city and how we envisioned the mall at the time,” Maybanks said.

Denlinger said he was nervous waiting for the verdict. When it came back in under three hours, he didn’t know what to expect.

“All I could think of was Janelle and John Stonebraker,” he said. “I prayed for them. I was extremely nervous, followed by extreme relief.”

The verdict: Burns was guilty of first-degree murder. The prosecution team waited to talk to the Stonebrakers.

“We were patting ourselves on the back,” Denlinger said. “I normally don’t like to do that but it was OK in this case.”

He said he also thought about the other family in the courtroom. The Burns family members he met had been nice and cordial to him. Burns’ wife was “quite decent” when he was in her home with a search warrant for computers.

John Stonebraker said last week that when he gave Denlinger a hug after the verdict, “I could see relief and great emotion in his eyes. It seemed like we bonded somehow, almost like teammates after a hard fought contest. Hard to describe.”

Janelle Stonebraker said she knew Denlinger took this “very personally — it’s not just a job to him. He was invested.”

She and her husband said they appreciated the department’s efforts to solve this case and the generations of officers and investigators who never gave up over the last 40 years.

Denlinger’s father and mother, along with wife Nicole and one of his four children came to the closing arguments. His kids who could not make it that day were sent text messages, saying they were proud of him.

Denlinger said that at some point he hopes to “pull the drain plug” — motioning to his ear — and let all the Martinko case file out and “put something else in my head.” But admits that will be difficult.

When he went back to work after the trial, he was hoping to “take a deep breath, relax and let the stress float away.”

But when he returned it was back to “cold case Thursdays” — the day Smith comes to the department, armed with doughnuts, to work cold cases with Denlinger.

“We couldn’t shut it down,” Denlinger said. “Me and J.D. went out to try to collect DNA on a different cold case. I don’t envision us relaxing any time soon.”