[Science of reading crime] ① The secret of DNA analysis that reveals the reality of ‘Busan spinning kick’

A man's DNA was found in the underwear of a sexual assault victim. However, it was difficult to determine who the traces belonged to. This is because the two men at the scene of the incident had identical paternal chromosomes.

In this case, which occurred in February 2023, the National Institute of Forensic Science (National Forensic Service) analyzed the underwear of victim A and detected Y chromosome DNA.

Men with the same paternal lineage could obtain the same Y chromosome analysis results, so it was difficult to identify the defendant based on these results alone.

The court declared the defendant not guilty in the first trial, saying that the defendant could not be identified using this DNA alone.

At the appeal trial, the prosecution requested a re-analysis from the DNA analysis room of the Supreme Prosecutor's Office (now the Public Prosecution Office) at the time.

The examiners expanded the scope of collecting samples from underwear and examined them again.

As a result, a semen reaction that was not confirmed in the previous analysis and autosomal DNA that could identify the defendant were confirmed.

The appeals court overturned the first trial ruling and sentenced the defendant to two years in prison.

Park Soo-jeong, a researcher at the Public Prosecution Service's DNA analysis office, likened the process of examining evidence with various traces to sifting grains of different sizes through a sieve.

Researcher Park said on the 13th, "At the scene of the incident, there are various traces mixed together, such as soybeans, red beans, and millet." He added, "The Public Prosecutors' Office's analysis office places more importance on precise analysis or re-evaluation using a small sieve."

This means that even if the evidence has been analyzed once, traces that were not previously identified can be found depending on which part is examined again.

◇ DNA found inside jeans… The reality of ‘Busan round kick’ is revealed

In the so-called ‘Busan roundhouse kick’ case, the results of re-analysis by the DNA analysis room of the Supreme Prosecutors’ Office at the time were used to reveal the damage from sexual crimes.

The Busan roundhouse kick incident is an incident in which a man in his 30s, Mr. Lee, chased after a victim who was returning home from Seomyeon, Busanjin-gu at around 5 am on May 22, 2022, with the intention of sexually assaulting her, and assaulted her by striking her in the back of the head.

Mr. Lee was indicted on attempted murder charges and sentenced to 12 years in prison in the first trial. In the appellate trial, the issue was whether or not a sexual crime was attempted at the time of the crime.

The National Forensic Service found the suspect's Y chromosome DNA in evidence requested by the police, but this alone did not confirm the charge of sexual assault.

The DNA analysis room, which received a request from the court for a re-evaluation, again examined the jeans worn by the victim.

Researchers turned the pants over and collected samples from various areas, including the inside, and detected the defendant's DNA from areas such as the waist, thighs, and calves. DNA, such as skin cells or body fluids, was also found on the inside of the jeans.

Researcher Lee Han-cheol explained, "We divided the victim's pants into sections and intensively sampled areas that could contain the suspect's DNA in the event of a sexual crime."

As evidence supporting the rape charge was revealed through DNA analysis, the prosecution changed the indictment to a charge of attempted rape and murder. The appeals court sentenced Lee to 20 years in prison, and the sentence was confirmed by the Supreme Court.

In addition, there are cases where 80 pieces of drug case evidence were analyzed to identify four additional people involved in the case in addition to the woman originally designated as a suspect, and there were cases where a check stored in a bank was analyzed to identify the culprit in a home invasion theft case where the suspect denied the crime.

Researcher Park Soo-jeong said, "When the evidence that has gone through the first analysis at the National Forensic Service is handed over to the Public Prosecution Office, we get another opportunity to analyze it. If DNA is not found even then, there is no next time."

He continued, “Evaluators always conduct analyzes with the mindset that it is the last time,” and added, “We conduct analyzes with the belief that if we cannot find the DNA, no one will be able to find it.”

◇ “Technology can only be developed through cross-verification… The Public Prosecution Service’s appraisal function must be maintained.”

As the investigative function of the prosecution was abolished in the past, the organization and functions of the former Supreme Prosecutor's Office's Scientific Investigation Department were also reduced and reorganized. The Forensic Science Planning Office of the Public Prosecution Service currently retains forensic science functions such as DNA and forensic chemistry analysis and psychological analysis.

Among these, there are voices from some in the political circles that DNA analysis should be integrated, saying that it overlaps with the functions of the National Forensic Service, but researchers at the Public Prosecution Service's DNA analysis office emphasized that there is a clear difference in the roles and purposes of the two organizations.

While the National Forensic Service specializes in confirming large amounts of DNA at a high speed, like the police's initial investigation, the Public Prosecution Service's DNA analysis room has the advantage of looking into details through detailed tests.

Researcher Oh Hye-hyeon said, “It’s not that ‘the National Forensic Service is bad at it, and the Public Prosecution Service’s DNA analysis room is good at it,’ but it’s about collecting different samples,” and added, “It is necessary to look at the case from different perspectives.”

In response to the opinion of some political circles that there is no need for another agency to re-evaluate the same evidence in one case, he emphasized the need for re-evaluation, saying, "When the suspect and victim disagree on the results of the analysis, sufficient analysis must be conducted so that no further complaints arise."

In order to increase the reliability of the appraisal results, the opinion was also expressed that the primary appraisal agency should not be in charge of re-appraisal.

Researcher Lee Han-cheol said, "The National Forensic Service showed that DNA was not detected as a result of the first analysis, but would you believe it if the same agency said it was detected during the second analysis?" He added, "If the person who approved the first analysis is a higher-ranking person than the person who approved the second analysis, we need to consider whether it may not affect the analysis results."

Researcher Park Soo-jeong also emphasized, “Technology can be developed only when two or more organizations cross-verify.”