[Criminal Profiling] ① Used for Violent Offenders like Jeon Juhwan... "96% Accuracy"

Providing Multidimensional Psychological Information... A Concentration of Advanced Technology
Offering Clues to Violent Cases Including the 'Donggeonyeo Murder' by Lee Gi-young

As major violent crimes such as murder and arson continue to increase daily, cases solved through forensic science are also on the rise. Advanced forensic investigations provide crucial leads in cases where clear criminal evidence, such as tools used in murder or arson, cannot be secured or when it is difficult to determine the truthfulness of a suspect's statement.

According to the Supreme Prosecutors' Office on the 27th, the use of integrated psychological analysis (including psychophysiological tests, EEG tests, behavioral analysis, and clinical psychological tests) in actual investigations is increasing. Except for 2020, when face-to-face investigations decreased due to the spread of COVID-19, the number of times integrated psychological analysis was used in investigations has exceeded 60 annually from 2019 through last year. Psychophysiological tests, commonly known as "lie detectors," have been utilized in the thousands each year from 2018 to last year.

Integrated psychological analysis applies two or more psychological analysis techniques among psychophysiological tests, EEG tests, behavioral analysis, and clinical psychological evaluation, and comprehensively analyzes and presents the results to reduce error rates and provide multidimensional psychological information.

The Supreme Prosecutors' Office Psychological Analysis Division conducts integrated psychological analyses upon requests from various prosecutors' offices to identify suspects' cognitive and personality traits, psychopathy status, and risk of recidivism, enabling the use of objective sentencing data during investigation and trial stages. Representative cases where integrated psychological analysis revealed psychopathy or risk of violent crime recidivism include Lee Gi-young, who murdered a taxi driver and his cohabiting partner; Jeon Ju-hwan, who killed a station attendant at Sindang Station; and Kang Yoon-sung, who damaged his electronic ankle bracelet and murdered two women.

Bang Cheol, Head of the Psychological Analysis Office at the Supreme Prosecutors' Office (left), is demonstrating a lie detector test experiment on reporter Heo Kyung-jun at the Psychological Analysis Office of the Supreme Prosecutors' Office while explaining the details. Photo by Heo Young-han younghan@

◆25 Prosecutors' Offices Equipped with 'Lie Detectors'... False Statements Not Accepted

The prosecution has equipped 25 prosecutors' offices with lie detectors and actively uses them in investigations. There are 23 professional examiners certified by the American Polygraph Association (APA). Although lie detector results are not directly accepted as evidence in court, clinical results reported to the APA show an accuracy rate of about 90%. Field studies based on practical criminal case data have recorded an accuracy of 96%.

Lie detectors measure changes in autonomic nervous system responses (such as respiration, blood pressure, pulse, and skin electrical response) caused by lying through psychophysiological testing devices and infer the truthfulness of statements. The use of lie detectors is increasing in cases lacking physical evidence, such as child abuse and sexual violence.

There have been many cases where confessions obtained through lie detectors or results accepted as evidence helped solve cases with insufficient physical evidence. In one case where a suspect raped a disabled mother and daughter living next door, the prosecution used a lie detector to reveal that the suspect's denial was false. This statement was accepted as evidence in court, resulting in a seven-year prison sentence.

A prosecution official explained, "The only direct evidence in the rape case was the victim's testimony, but since the victim was disabled, the consistency of the testimony was weak. It was difficult to indict the suspect based solely on the victim's statement, so we conducted a lie detector test, which showed all false responses. Based on the lie detector investigation, despite only having indirect evidence, the suspect was indicted and received a heavy sentence."

◆Prosecution’s ‘Integrated Psychological Analysis’ Provides Smoking Gun in Major Cases

The Supreme Prosecutors' Office Psychological Analysis Division developed the integrated psychological analysis technique in 2006, combining various psychological analysis methods such as psychophysiological tests, EEG analysis, behavioral analysis, and statement analysis. Since then, it has provided systematic and scientific analyses of suspects in violent crimes, offering multidimensional psychological information. Psychological analysts at the Supreme Prosecutors' Office clarify the truthfulness of statements and psychological and personality traits of those involved in cases, providing clues to solve cases. This differs from police profilers who analyze evidence left at crime scenes to identify criminal characteristics and narrow down investigations.

Recently, integrated psychological analysis has played a significant role in solving previously unsolved violent crime cases. In a case where a suspect killed his mistress's wife by making her drink soju laced with cyanide, clinical psychological evaluation concluded that the suspect had a strong theatrical tendency and was highly likely to explosively express anger when frustrated. The court accepted the analyst's testimony as evidence and sentenced the suspect to 25 years in prison. In another case where a suspect stabbed his cohabiting victim in the side with a weapon during an argument, integrated psychological analysis revealed that the suspect's statement denying memory of stabbing the victim was false.

The Supreme Court has not yet issued a clear stance on the evidentiary value of integrated psychological analysis results, but lower courts are increasingly accepting them as evidence of guilt or including the analysis results in their rulings.

Bang Cheol, head of the Supreme Prosecutors' Office Psychological Analysis Division, said, "Integrated psychological analysis incorporates cutting-edge technology. It is used in most recent violent crime cases. Although records are reviewed before the examination, the investigation and evaluation are conducted completely separately without considering the direction of the investigation, so the examination is very objective and fair."