“It’s absolutely amazing. If they (the Cedar Rapids police) hadn’t preserved that evidence, we wouldn’t be here 40 years later,” said Stonebraker, 70, standing outside the Scott County Courthouse on Monday after Jerry Burns, 66, of Manchester, was convicted in her sister’s fatal stabbing.

Many had been accused of the crime over the years, and “we don’t know exactly the why’s,” but she and her husband, John, 74, said they were pleased with the first-degree murder verdict.

“I wished our parents could have lived to see this,” said Stonebraker, who now lives in Florida.

The seven women and five men on the Scott County jury needed less than three hours to convict Burns, who has lived with his family in Manchester and built a business for the last 40 years after ending Martinko’s life Dec. 19, 1979.

Martinko was found dead in her family’s Buick, parked near J.C. Penney at Westdale Mall. She had attended a choir banquet and then went to the mall to get a coat her mother had put on layaway.

According to testimony, the teen was stabbed 29 times. A pathologist said the fatal stab wound was to the sternum, which penetrated her aorta, and she bled to death.

A public genealogy database, GEDmatch, helped authorities identify Burns as a match to DNA found on the back of Martinko’s black dress and car gearshift. Burns was arrested Dec. 19, 2018 — on the 39th anniversary of her death.

Testimony showed less than one in 100 billion chance someone other than Burns would have the same DNA profile, Iowa Division of Criminal Investigation criminalists said.

The trial was moved to Scott County because of pretrial publicity.

When the verdict was read, John Stonebraker hugged his wife. After the jury was released, they hugged their son, Robert Stonebraker, his wife, a cousin and other friends.

The family cried with relief after the verdict, recalling Michelle, who was described as “kind, sweet, funny, pretty and smart.”

John Stonebraker choked up as he praised the police and said, “We left Cedar Rapids but Cedar Rapids didn’t leave us.”

He said his family didn’t want to have a celebration because the Burns family is experiencing its own pain and heartbreak.

The Burns family filled one side of the courtroom every day of the trial. They were emotional but quiet as they heard the verdict.

Burns faces life in prison without parole. His sentencing isn’t set yet.

First Assistant Linn County Attorney Nick Maybanks said late Monday he laid out a scenario of what happened to Martinko, based on the prosecution’s theory and the evidence, because he knew the jury wanted to know why or how it happened.

In closing arguments, Maybanks told the jury Burns, a young man back then, was Christmas shopping at the mall and he followed her out with a premeditated act in mind. He later would lament “that DNA wasn’t a thing back then” to a Linn County Jail cellmate.

Martinko walked out of the mall to her car and unlocked the back door to put a shopping bag inside, Maybanks said in his closing. The killer “had to act fast” before she drove away. He opened her car door and struck her head with the knife handle. Martinko fell back on the car seat. He held her down as she fought. “Her fear and terror kicks in,” Maybanks said.

The killer becomes more aggressive to stop her struggling and plunged the knife into her chest multiple times, Maybanks said. He had to end what he started. Martinko tried to move away from the knife, and Burns cut himself during the assault. He considered driving her car, but he’s bleeding and he has to get to his car.

Burns put the Martinko car into park and smeared her blood and his on the gearshift, Maybanks said. He then drove back to Manchester within the hour.

Maybanks, after the verdict, said Burns has been carrying this secret for 40 years. But he let it leak about how he kept it to Matthew Denlinger, Cedar Rapids police investigator, when he talked about “blocking out” things.

“That’s why (in closing) I said people can be different things — capable of loving and wonderful things, and some are capable of sordid and cruel acts,” Maybanks said.

Maybanks commended Denlinger for his diligent and determined work on this cold case. “We were lucky to have Matt.”

Maybanks said this was only the second trial in the country to result in a guilty verdict for a case solved through genetic genealogy, and pointed out that Denlinger, as well as “many generations of Cedar Rapids officers” collected the evidence and pursued leads.

“This was a clear-cut case,” Maybanks said in response to the jury’s short deliberations. “It was a combination of science and Burns’ statements that we believe overwhelmingly establish his guilt.”

Defense attorney Leon Spies, in his closing, tried to put doubts in the jurors’ minds about how the evidence was mishandled over the years and suggested there could have been cross-contamination.

He also argued Burns never admitted to anything and told law enforcement he didn’t know Martinko or how his DNA could be at the crime scene. Spies said there was “lack and failure” of the evidence in this case to convict because it causes reasonable doubt.