[Case File] There Is No Perfect Crime... 'DNA' Solving Cold Cases

Serial Killer Lee Chun-jae Confesses Before DNA Evidence
Also a Crucial Clue Proving Yoo Young-chul's Crimes
Child Molester Kim Geun-sik Re-arrested One Day Before Release
'Key' to Unveiling Truth in Cold Cases

Lee Chun-jae, who committed a series of murders in the Hwaseong area of Gyeonggi Province from the 1980s to the 1990s. While serving his sentence, DNA comparison revealed that he was the true culprit of these cases. [Image source=Yonhap News]

[Asia Economy Reporter Han Seung-gon] Scenes like the following are commonly seen in TV dramas or crime movies. A disheveled detective apprehends and interrogates a prime suspect one hour before the statute of limitations expires. If the DNA comparison results from the National Forensic Service arrive an hour late or conclude that the evidence is inadmissible, the case falls into a dead end. Then, a junior detective rushes into the interrogation room, out of breath, delivering news that the National Forensic Service's DNA comparison confirms the suspect as the culprit. The suspect then confesses as if resigned to everything.

Nowadays, so-called 'DNA investigation' techniques are easily seen in movies, but their practical introduction and establishment are known to have occurred in the 1990s. Because of this, some brutal crimes that occurred before then were not properly solved. This is why many cold cases are concentrated in the past.

However, things are different now. DNA investigation techniques not only secure clear evidence but also solve past cold cases. Recently, a prime suspect in a previously unsolved sexual assault case was apprehended by the police. This case remained unsolved because there were no witnesses or other evidence at the time to identify the suspect.

According to Jeju Eastern Police Station on the 10th, a man in his 40s, Mr. B, was booked on suspicion of special rape of Mr. A around 2008 in Jeju. Earlier, Mr. B was investigated for another case, and during that process, DNA comparison with the National Forensic Service database confirmed that Mr. B's DNA matched the cold case from 14 years ago. However, the court dismissed the warrant due to no risk of flight or evidence destruction. The police are reviewing reapplication for an arrest warrant through supplementary investigation.

[Image source=Yonhap News]

DNA Investigation Preventing 'Perfect Crimes'... How Are Culprits Caught?

The unique 'DNA fingerprint' used to identify culprits is a sequence where base pairs repeat without genetic information. It is used to identify individuals like fingerprints. DNA consists of four bases (guanine, cytosine, thymine, adenine). The probability that a specific sequence in the nuclear DNA of one person's cells matches another's is one in 10 to the 15th power. This means the chance of one person's DNA matching another's is almost zero.

DNA collected at crime scenes undergoes a process called 'Polymerase Chain Reaction' (PCR). This process is essential because DNA found at crime scenes is often damaged or incomplete, making it difficult to compare or identify suspects' DNA with the raw DNA collected at the scene.

The key in the PCR process is 'amplification' (meaning increasing the range or size of an object). To use DNA for genetic analysis, a sufficient amount must be secured. Then, equipment like an automated gene sequencer is used to determine the genotype.

Actively Used in Investigations... Serial Killer Lee Chun-jae's Confession

The PCR process used to catch criminals was developed in 1983 by American biochemist Kary Mullis, who revolutionized biological research and was awarded the Nobel Prize in Chemistry in 1993. However, it took a long time before police began using it as an investigative technique. In Korea, DNA investigation techniques were introduced in 1989. At that time, such methods were not widespread, and related technologies like DNA collection were in early stages, making DNA analysis difficult.

Meanwhile, serial killer Lee Chun-jae committed brutal crimes in the Hwaseong area of Gyeonggi Province during the 1980s and 1990s, evading the investigation net, which is a tragic reality when recalling the victims.

Eventually, Lee Chun-jae admitted his crimes in the face of DNA investigation. After serving a life sentence for killing his sister-in-law in 1994, he had firmly denied the serial murder charges. However, when the police presented DNA analysis results from evidence, he confessed. The National Forensic Service confirmed identical DNA in evidence from the 5th, 7th, and 9th cases. On November 2, 2020, Lee Chun-jae testified as a witness in the retrial of the 8th case, stating, "I am the real culprit of the Hwaseong serial murders."

'They Will Definitely Be Caught'... Solving Both Current and Past Crimes

Another example of solving long-term cold cases like the Lee Chun-jae case exists. In July 2001, a man broke into a home, brutally assaulted, and sexually assaulted the victim. At the time, police secured the perpetrator's DNA from a towel with semen but could not identify a match and failed to find the culprit. Then, in July 2021, they confirmed that the DNA of a registered rapist and murderer in the database matched the DNA from the 20-year-old rape case and arrested him. This was five months before the statute of limitations expired.

Similarly, in 1997, a 20-year-old woman was sexually assaulted and killed in the parking lot of a golf practice range in Daechi-dong, Gangnam-gu, Seoul. During a 2020 reinvestigation, DNA from the victim's body matched that of Mr. C, who was serving a life sentence for robbery and murder, leading to the arrest of the culprit after 22 years.

DNA investigations are used to dismantle suspects' alibis or serve as clear evidence. In the 2004 Yoo Young-chul serial murder case, DNA types of victims were detected on blunt weapons and evidence from an officetel, providing grounds and decisive evidence to judge the crime circumstances. Also, in the 2018 Gwangju group assault case, DNA experts discovered additional evidence such as blood-stained branches during on-site inspections, securing evidence and verifying the credibility of victims' testimonies.

There are also cases where a prisoner about to be released was identified as a suspect in another case and re-arrested. Child sex offender Kim Geun-sik was re-arrested on October 16, one day before his release, for forcibly molesting a child under 13 in Incheon in 2006. The prosecution reviewed DNA analysis data of an unidentified perpetrator attached to an unsolved sex crime case from 2006 and confirmed a match with Kim Geun-sik's DNA. Ultimately, Kim had no choice but to confess. Previously, Kim had been sentenced to 15 years in prison for sexually assaulting 11 minors in the Seoul metropolitan area from May to September 2006 and was serving his sentence at Anyang Prison.

Summarizing these cases, DNA investigation techniques show that not only current crimes but also past offenses cannot be perfect crimes. Investigation statistics confirm that criminals will inevitably be caught. According to the annual operation report of the DNA Identity Information Database Management Committee, since the enforcement of the 'DNA Identity Information Use and Protection Act (DNA Act)' in 2010, 6,369 cold cases have been reopened through DNA matches over 11 years.

Among the types of cold cases solved through DNA, theft (4,084 cases) was the most common, followed by sexual violence (1,015 cases), robbery (264 cases), drugs (165 cases), violence (137 cases), arson (43 cases), and murder (38 cases). Even at this moment, many cases are being solved through DNA comparison. As DNA scientific analysis techniques advance, the saying 'there is no perfect crime' and that DNA is the key to unraveling 'dark crimes' (crimes that occur but whose suspects are unidentified and thus not recorded in official statistics) is becoming more widely accepted.