DAVENPORT, Ia. — For nearly 40 years, the family of slain high schooler Michelle Martinko waited for an arrest. Then for proof. Then for a verdict.

The wait ended Monday, when a jury convicted Jerry Lynn Burns of first-degree murder in the 1979 stabbing death of 18-year-old Martinko. It was a case, Cedar Rapids Police Chief Wayne Jerman said, “that has haunted our community for decades.”

“We don’t exactly know the whys and some of the details, but we definitely know who did it, and that was terribly important to us,” Janelle Stonebraker, Michelle Martinko’s older sister, said after the verdict was read. “I wish my parents could be here to see this.”

The sisters’ parents died more than 20 years ago, Albert Martinko in 1995 and his wife, Janet, in 1998.

Burns, 66, was arrested at his Manchester, Iowa, business on Dec. 19, 2018 — the 39th anniversary of Martinko’s death — and charged with first-degree murder in Martinko’s slaying. He pleaded not guilty to the charges.

After listening to almost two weeks of testimony, a jury of seven women and five men returned the guilty verdict after deliberating just shy of three hours. 

Previous coverage: Decades after fatal stabbing, Michelle Martinko’s family comes face-to-face with her alleged killer

Stonebraker sat in the front row of the courtroom, flanked by her husband, John, and oldest son, Robert. After the verdict was read and court was adjourned, they stood and embraced as Martinko’s friends around them wept.

Across the aisle, the benches behind Burns were packed to the brim. His family and friends remained seated after Martinko’s family left the courtroom.

John Stonebraker said the three hours it took the jury to reach a verdict was indicative of the strength of the case. He and his wife, who now reside in Florida, said they were grateful for the Cedar Rapids community’s commitment to the case over the past 40 years.

“We left Cedar Rapids, but Cedar Rapids never left us,” he said, choking up outside the courthouse while his wife nodded in agreement.

Defense attorney Leon Spies declined to comment immediately following the verdict.

Martinko was found dead in her parents’ Buick in the parking lot of Westdale Mall in Cedar Rapids early on the morning of Dec. 20, 1979, “curled onto the passenger seat floorboard, stabbed multiple times and bloodied from the wounds she sustained,” first assistant Linn County attorney Nick Maybanks previously told jurors.

Leads in the case resulted in dead ends until investigators used a genetic genealogy website to connect Burns’ DNA to the crime scene. Decades of technological advancements ultimately allowed experts to construct a partial male DNA profile from a blood scraping on the gear shift of the Martinko family car and a blood stain on the back of Martinko’s dress.

After turning to GEDmatch, a commercial genetic genealogy site, investigators narrowed their suspects to three brothers, all in Iowa. Investigators matched the male profile at the crime scene to DNA on a straw Burns left behind at a Manchester Pizza Ranch.

“The people in law enforcement take on their duty and their task seriously,” Maybanks told the Des Moines Register, part of the USA TODAY Network, after the verdict. “When they commit to helping a family, as in this case, looking into the eyes of parents who lost an 18-year-old girl and said, ‘We’re going to find the answer to what happened to her,’ that the public can trust that they’re going to do that, even if it takes generations to do it.”

“This is Michelle’s day,” he added. “She finally got justice.”

In closing arguments Monday, Spies repeated a phrase from his opening arguments: “Genetic information tells us much about what we are, but not necessarily who we are or where we’ve been.”

He rebutted some of the prosecution’s factual claims, insisting that there wasn’t substantial evidence that Burns’ DNA was retrieved from his blood, noting previous testimony indicating it could have been saliva or even transferred skin cells and that the presence of DNA in itself could not implicate Burns.

While Burns’ attorneys didn’t offer an alibi for where he was the night of Martinko’s murder, Spies did suggest that since Burns had been to Westdale Mall with his family before, DNA he left behind at the mall could’ve transferred to Martinko while she was at the mall Dec. 19.

Maybanks noted that even though Martinko interacted with at least half a dozen friends the night of her death, including at the mall, none of their DNA was found at the crime scene.

Maybanks recapped Monday how witnesses in the two weeks prior outlined an extensive chain of custody of the evidence to ensure no new DNA could have been introduced into the packages containing Martinko’s bloodied clothes and pieces of the car.

The only way Burns’ DNA could’ve ended up in two spots in the crime scene, Maybanks concluded, was if Burns was the murderer.

In the end, the jury agreed.

Burns’ sentencing is likely to be scheduled for early April, though a date has not been set, District Judge Fae Hoover said. The mandatory penalty for first-degree murder in Iowa is life imprisonment without the possibility of parole.

Jerman, Cedar Rapids’ police chief, credited police and investigators who “showed tenacity and dedication” over the four decades it took to take the case to trial, and the Linn County Attorney’s Office for its role in Burns’ arrest and prosecution.

“For Michelle’s family and friends, we know that the pain of losing a daughter, sister or friend will never go away,” Jerman said. “You and Michelle will forever be in our thoughts, and we are eternally grateful for your support, trust and confidence over the many years.”

Follow reporter Anna Spoerre on Twitter at @annaspoerre.

‘Puro cash’:Latinos are opening more small businesses than anyone else in the US

Julian Assange:Why he matters more than you think