[Exclusive] Police Missed the Original File, Prosecution Salvaged Case with Forensics [Jang Yoonki Ignites Prosecutorial Supplementary Investigation] ②

Copy of Recording File, Not Original, Submitted as Evidence
Critical Weakness for the Victim

A case has been identified in which a police oversight in evidence collection nearly became a critical weakness during trial proceedings. The police failed to secure the original recording file from the victim's mobile phone and instead submitted only a copy. The defendant seized on this point during trial, arguing, "A recording file without the original cannot be trusted." This case, which could have remained unsolved, ultimately resulted in a guilty verdict after the prosecution conducted supplementary investigations, including digital forensics.

Exterior view of Suwon District Court and Suwon High Court. Photo by Yonhap News

According to a comprehensive report by The Asia Business Daily on July 9, the 12th Criminal Division of Suwon District Court (Presiding Judge Park Geonchang) sentenced a man in his 30s, identified as Mr. A, to one year and six months in prison and ordered his immediate detention in court on June 25, on charges of quasi-rape. Mr. A was accused of committing a quasi-rape offense against Ms. B, a woman in her 30s whom he first met via a chat application in June 2024, after drinking alcohol together at her residence when she was heavily intoxicated.

Mr. A denied the charges during the trial. The main issue was a recording file containing a conversation in which Mr. A apologized to Ms. B and effectively admitted to the crime immediately after the incident. The investigating officer did not obtain the original file directly from Ms. B's mobile phone but instead received it via the agency-issued mobile device and submitted this as evidence. Later, when Ms. B replaced her mobile phone, submission of the original file became impossible.

During the trial, Mr. A's legal team challenged the fact that the recording file was only a copy. They argued that during the file transfer, the file extension changed and the frequency band was reduced due to so-called transcoding, making it impossible to verify whether the file had been edited and calling into question its authenticity. The police's failure to secure the original file thus became a key part of the defendant's defense strategy.

The prosecution responded by conducting an additional analysis at the National Digital Forensic Center (NDFC) Voice Analysis Lab of the Supreme Prosecutors' Office. The NDFC analyst stated that even if the frequency band and other parameters had changed, if any editing had occurred, traces would be detectable in the preserved file; however, no signs of alteration or tampering were found in this file. The prosecution submitted an opinion letter on the analysis results to counter the defendant's claims.

The prosecution also used the testimony of the investigating officer to establish the process by which the recording file was submitted, stored, and admitted as evidence. Based on this, the court accepted the prosecution's arguments and imposed a custodial sentence on Mr. A.

The legal community has evaluated this case as an example demonstrating that insufficient evidence collection at the investigative stage can lead to critical gaps during trial. Since minor oversights at the police stage can jeopardize both victim protection and the clarification of the facts, experts stress the need for a system of external review and supplementary measures to identify and address any gaps in the case record after it is handed over.

This content was produced with the assistance of AI translation services.