[Criminal Catching Psychological Analysis]② Experiencing the 'Geojitmal Tamjigi'... Couldn't Escape Even When Pressing Toes Hard

Our reporter personally experienced 'lie detector and brainwave tests'
Test results revealed 'manipulation myths'... Testing equipment cannot be deceived

Can a suspect's false statements be detected through psychological analysis such as lie detectors and brainwave tests? Could a strong-hearted person with almost no psychological disturbance render lie detectors useless?

Investigations using advanced equipment like lie detectors have become routine in investigative agencies such as the prosecution and police. However, most people still harbor doubts about identifying criminal suspects based on psychological analysis tools like lie detectors rather than clear physical evidence.

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@

A reporter from Asia Economy, skeptical about the reliability of lie detectors, visited the Supreme Prosecutors' Office Psychological Analysis Room on the 13th to experience lie detector and brainwave tests firsthand. With the mindset that one can survive even in a tiger's den by staying alert, the reporter headed to the prosecution's proud psychological analysis testing room.

The testing equipment was surprisingly simple. In front of a desk with two monitors, there was a black leather chair connected by several wires and a CCTV installed on the opposite wall. Upon sitting, two bands pressing the chest and abdomen were fastened. Clip-type sensors were attached to the left hand's index, middle, and ring fingers. On the right arm, a device resembling a blood pressure monitor was attached. Looking at the equipment on the body, it seemed to boast the capability to detect every physical change.

"Are you a man?" "Is your name OOO?" Several ordinary and obvious questions were repeated, and when answering "yes," the pulse graph remained calm. Bangcheol, head of the Supreme Prosecutors' Office Psychological Analysis Room, instructed, "From now on, please answer all questions with 'no.'"

"Are you married?" (Examiner) "No" (Reporter)

The dramatic scenes of catching criminals using psychological analysis like lie detectors, often seen in movies or dramas set in investigative agencies, instantly seemed like a fantasy.

Suddenly giving false answers, although breathing and pulse did not quicken, the graph fluctuated wildly. Even though the reporter was informed beforehand to lie, suddenly lying caused considerable pressure. It felt like being ambushed unexpectedly, and the thought of trying methods to neutralize the lie detector arose.

"I've heard that physical stimulation can cause test results to be incorrect." (Reporter) "Try it once." (Examiner)

As seen in movies, the reporter tightened the anus at the moment of lying. The graph sharply spiked and then dropped exactly at that moment. The chair had sensors detecting the examiner's movements, so the abnormal reaction appeared directly on the graph. Trying to stimulate by moving toes without any equipment attached was also detected, as the toe movements were clearly visible on the CCTV installed in front, revealing the attempt.

Brainwave testing equipment in the Psychological Testing Office of the Supreme Prosecutors' Office. Photo by Younghan Heo younghan@

After being helplessly defeated by the lie detector test, the reporter moved to the brainwave testing room. The brainwave test room was about the size of a coin karaoke booth where you insert coins and sing, furnished only with a chair, desk, several buttons on the desk, and a monitor opposite. Despite the brainwave testing equipment costing over 100 million won, nothing seemed particularly special. For the test, the reporter wore a headgear-like device with dozens of wires connected, covering the entire head except the face.

The test involved identifying stolen items by showing several photos of items not stolen and measuring brainwave responses when the actual stolen item appeared.

"Assuming you stole a black wallet, press a different button when the black wallet appears on the screen." (Examiner)

The principle was simple: press button A when other wallets appeared on the monitor and button B when the black wallet appeared. After several repetitions, the test ended, and the graph recording the statistics showed a single result.

Brainwaves showed a consistent pattern for wallets of other colors but noticeably spiked only when the black wallet appeared. The examiner explained that the actual test shows the same screen at least 60 times to identify items related to the crime, and with repeated tests, an average graph value emerges with consistent responses.

The prosecution has solved major violent crimes such as the Gwangmyeong family triple murder case, Sindang Station clerk murder case, and taxi driver and cohabitant murder case through this integrated psychological analysis.