DNA analysis, thousands of surnames, and two years of meticulous work — this is how the investigation that led to a breakthrough in the case of the murder of 13-year-old Iza Strzałkowska from Gdynia looked. Genetic genealogy played a key role — a method that allows searching for not the criminal himself, but his relatives. Thanks to this, investigators narrowed the list of suspects down to three men.
The method combines DNA research with classical genealogy. Specialists compare the genetic material found at the crime scene with databases of individuals who voluntarily underwent DNA tests to explore their ancestry and allowed the use of the results in criminal investigations.
If there are no matches with the perpetrator himself, distant relatives can be discovered—even those connected by common ancestors who lived several centuries ago. After that, researchers reconstruct family lines and gradually narrow down the circle of people who may be related to the case.
In an interview with Radio ESKA, genetic genealogist Marta Sobota, who worked on the investigation, explained that the task was not to directly search for the murderer.
“We are not looking for a criminal, but for his distant cousins. In this case, kinship was analyzed at the level of five to six generations back. We were talking about common ancestors who lived at the turn of the 17th and 18th centuries,” she said.
In fact, specialists had to go back more than 200 years and then trace the fates of all the descendants of these families.
A Tree for 10 Thousand People
The most labor-intensive stage was the creation of a giant family tree, which included about 10,000 people. Researchers analyzed each branch of the family to determine who might match the genetic profile left by the criminal.
“It was necessary to go down all the branches and find all the descendants,” explained Marta Sobot.
After months of work, the circle of possible suspects has been narrowed down to three men.
“This is not an accusation, but a very strong hook”
The expert emphasizes that genetic genealogy does not determine the guilty party by itself.
“We do not say: ‘this is a criminal.’ We say: ‘this is a very strong lead,’” noted Sobotka.
The further work was already in the hands of the police and prosecutors, who were investigating each of the three men who came under the scrutiny of the investigation.
Michał S. confessed to murder
One of these three men turned out to be Michał S. He was arrested in connection with the murder of 13-year-old Iza Strzałkowska.
According to the investigation, the man confessed to committing the crime, but refused to provide further explanations.
The use of genetic genealogy in this investigation is considered an important achievement in Polish forensics. Until now, such methods have been applied very limitedly in the country.
Experts note that the successful resolution of the case of Iza Strzałkowska could set a precedent and assist in the investigation of other unsolved crimes from previous years, especially those where DNA samples have been preserved, but traditional investigative methods have not yielded results.
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