Jerry Lynn Burns will be serving life in prison without parole after he was found guilty of murder that occurred almost 40 years ago, thanks to DNA samples from an online ancestry service.

On December 19, 1979, an 18-year-old woman Michelle Martinko was found stabbed to death in the parking lot of a mall in Cedar Rapids, Iowa. The case soon turned cold for a number of years until 2006, when an investigator identified blood not belonging to the victim among the case files.

Last October 2019, Jerry Lynn Burns was arrested and was found guilty thanks to a familial DNA match. On August 7, Burns was sentenced to a life without parole.

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Finding a DNA Match on a Public Website

When the case was first investigated in 1979, there were limited leads and asked for the public's help. A representative for the local police department said that more than 200 people responded to their appeal for additional information that would help them move forward with the case. Police authorities also released a composite sketch from witnesses under hypnosis and later consulted psychics to help with the investigation.

The case grew cold in the following years, with Martinko's father passing away in 1995 and her mother in 1998.

It was in 2006, 27 years after the incident, that the investigation was reopened by a new investigator who looked at the case, later discovering blood not belonging to Martinko. From the sample, the police built a partial DNA profile of the suspect. It was encoded into the Combined DNA Index System (CODIS), the general term for the United States' DNA database from convicted felons and other evidentiary samples, as well as the software program that allows cross-checking from its records.

No match was found. In the course of investigation, more than 125 people underwent DNA swabbing to be compared to the sample found in the crime scene. After another 11 years, in 2017, a private company specializing in DNA phenotypes were tasked with drawing physical clues about the killer based on DNA samples, revealing different features from the composite sketch released in the 80s. The same DNA phenotyping company used their data and entered it into GEDmatch - an online service that compares DNA samples from files provided by different testing companies.

From the GEDmatch results, there was one match: a woman who shared DNA markers with the sample from the crime scene. The phenotyping company then started generating the woman's family tree and started narrowing down the suspects by secretly collecting DNA tests. The last set remaining included a group of three brothers who all grew up in Manchester, Iowa.

In October 2018, an investigator who was trailing Jerry Lynn Burns, one of the three brothers, saw him drink soda using plastic straw. After the straw was disposed of, it was recovered by the investigator, had it tested, and found that it positively matched the blood from the crime scene.

DNA Testing in Forensics

Forensic DNA analysis is a fairly recent investigative technology. In 1984, British geneticist Dr. Alec Jeffreys discovered similarities and differences between samples taken from family members of his lab technician. It led to the realization that DNA fingerprinting could be used to identify individuals.

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It was first used in a 1985 case to solve an immigration dispute, confirming that a British boy with Ghanaian ancestry was proven to be related to his other family members.

DNA evidence, especially for use in forensic science, requires a sample, mostly human tissue or fluids. Samples as small as one nanogram of DNA is enough to provide an individual's profile. In the United States, the 13-STR profile is commonly used. Scientists find a short tandem repeat (STR) in the sample. The Federal Bureau of Investigation has identified and widely uses, a set of 13 core STR loci.

These 13 core STR loci are compared between the sample taken from the suspect, to be compared with those found from the crime scene. If the two samples do not match, the suspect is excluded. However, if all 13 core STRs match, it has to be statistically recomputed to determine the frequency of this occurrence ever happening in the population. Nowadays, forensic scientists use the Hardy-Weinberg calculations to check the frequency for each STR.

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