Last year, prosecutors requested supplementary investigations for nearly one in seven cases returned to the police, marking the highest rate on record since the introduction of the supplementary investigation request rights in 2021. This statistic, reported by lawmaker Yang Bum-nam of the Democratic Party, shows that from over 750,000 cases sent by the police, prosecutors requested additional investigation for 110,623 cases, equating to approximately 14.7%. The continuing upward trend in case referral back to the police underlines both the increasing scrutiny and the ongoing tensions between the police and prosecutors over operational authority and responsibilities.

The rise in supplementary investigation requests reflects a complex interplay of factors, including the perceived inadequacy of police investigative capabilities and ongoing rivalries between the prosecutor's office and police investigators. For instance, the ongoing investigation into allegations against independent lawmaker Lee Chun-seok illustrates this dynamic, where a case initially referred to the prosecutor's office remains without indictment even after several months due to conflicting conclusions about the evidence. Reports suggest that the prosecutor's requests for additional investigations often consist of basic procedural matters, further pointing to the friction in communication and coordination between the two agencies.

The police recognize the necessity for supplementary investigation rights but are calling for improved collaboration to minimize delays stemming from case 'ping-ponging.' Recent high-profile cases, including that of former President Moon Jae-in's wife's alleged misuse of funds, have drawn public attention to the inadequacies of the current system. As the authorities navigate these complexities, there is an urgent need to reform and streamline the investigation process to enhance efficiency and accountability in handling criminal cases.