It was a cold case until 2018, when familial DNA identified a suspect 39 years after the crime who was charged, tried and convicted of her murder.

In October 2018, DNA was covertly collected from an Iowa man, Jerry Lynn Burns, and was found to match the sample discovered on Martinko's clothing.

[2] She did not have many close girlfriends or confidantes, which was speculated to be caused by jealousy from other students over her beauty and stylish clothes[11] or conflict over a boy she had dated.

[12] Martinko, who was a senior in high school when she was killed, had plans to attend Iowa State University to study interior design.

[16] On the evening of December 19, 1979, Martinko attended a banquet for the Kennedy Concert Choir at the Sheraton Inn in Cedar Rapids.

[9] After the event, she asked her friend and twirling squad teammate if she wanted to join her on a shopping trip to the Westdale Mall, which had recently opened, and where Martinko worked.

At 4 a.m., police found the Martinko family's tan and green 1972 Buick Electra in the northeast corner of the mall parking lot by a JCPenney.

[10] A police spokesman estimated that in the week after Martinko's murder, more than 200 people responded to the detectives' appeals in the news for information concerning the case.

A juvenile found carrying a knife was interviewed and ruled out in her murder, as was a shopping center employee who had told police that he enjoyed following women and ogling store mannequins.

[19] For some time, a prime suspect in Martinko's murder was a man who had, the month before, broken into a Cedar Rapids home, raped a woman at knifepoint, and threatened to kill her children.

[19][20] Controversy arose five months after the murder, after a woman who was driving by the mall parking lot in the early hours of December 20 came forward with information.

The woman communicated her information to the daughter of the secretary of the Public Safety Commissioner and believed that it would be passed on to police if it was important.

[21] On June 19, 1980, police released a composite sketch of a man believed to have killed Martinko, which they formed from descriptions provided by two witnesses under hypnosis.

[4] In the mid-1980s, Martinko's father filed a lawsuit against the owners of the Westdale Mall and claimed negligence in not providing "reasonable security" on the night of the murder.

[25] In 2018, the DNA phenotyping company took the data they had collected the year before and entered it into GEDmatch, a public genealogy website that has been used by law enforcement to solve other cold cases, most famously that of the Golden State Killer.

GEDmatch returned one person who shared DNA markers with the suspect in Martinko's murder, and it determined her to be likely the killer's second cousin once removed.

The company created a family tree starting with four sets of the woman's great-great-grandparents and reported that the killer was most likely descended from one of those couples.

[2] On October 29, 2018, an investigator observed one of the brothers, Jerry Lynn Burns, drink multiple sodas using a plastic straw.

Tests eliminated the other two brothers as suspects, but the DNA from Burns' straw matched the blood found on Martinko's clothing.

His trial was originally scheduled for October 14, 2019, but in September the defense requested a delay in order to gather more evidence and interview witnesses.

The defense also requested the trial be moved out of Linn County based on the amount of attention the case had received over the past four decades, as well as "pervasive and prejudicial pretrial publicity".

Investigators had reviewed Burns' 2018 internet searches and found that he regularly visited websites showing blonde women being raped, stabbed, and strangled, and which depicted sexual intercourse with murder victims.

"[34] The defense brought only one witness, a self-described forensic DNA consultant, who testified on the possibility that police could have mishandled the evidence.

[36] On February 24, 2020, after three hours of deliberation, the jury found Jerry Lynn Burns guilty of first degree murder of Michelle Martinko.

[37] On May 29, 2020, Burns' attorneys filed a motion asking for a new trial, claiming his constitutional and state rights were violated and that the court made a mistake in overruling the request for evidence to be suppressed.

[41] On March 31, 2023, the Iowa Supreme Court denied Jerry Lynn Burns' appeal and upheld his conviction.