Park Se-hyun, the head of the prosecution's special investigative team to probe the insurrection case, prepares during a press briefing held in Seoul on Dec. 8. (Yonhap)

South Korea’s two main law-enforcement bodies are vying to seize control over the investigation into President Yoon Suk Yeol’s martial law declaration on Dec. 3, with both prosecution and police conducting simultaneous investigations, rather than cooperating.

On Dec. 8, prosecutors proposed that the police form a joint investigative team, but the police rejected the idea, citing “credibility and fairness” as reasons. Police also asserted they have jurisdiction over the investigation into the insurrection charge based on the 2021 agreement between the prosecution and police.

"Insurrection falls within the scope of police investigations. If the prosecution handles it, there’s a risk of the case being dismissed in court due to procedural issues,” a representative from the Police’s National Investigation Headquarters said in a statement on Dec. 8.

Despite lacking a direct investigative right regarding insurrection, the prosecution set up a special investigation team on Dec. 7 before anyone else, comprising 20 prosecutors and 30 investigation officers. The majority of them worked on the 2017 investigation into ex-President Park Geun-hye.

Prosecutors insist on the legitimacy of their investigation because the police leadership is under investigation for controlling access to the National Assembly during the martial law attempt. Prosecutors also consulted on the issue with the Seoul District Court, which sided with the prosecution.

On Dec. 8, the prosecution placed the ex-Defense Minister under emergency arrest and filed an arrest warrant, which was approved by the Seoul Court on Dec. 10.

Police investigator is seen with a box of evidence after its attempt to search and confistication at the Presidential Office in Yongsan, Seoul, Dec. 11. (Yonhap)

To counter the prosecution's first-mover advantage, the police added more than 30 investigators to its existing 120-person investigation team, expanding the size of its investigation team to 150 people.

The current judiciary system gives the prosecution the authority to request, delay or dismiss police warrant applications.

Adding the complexity is an intervention by the Corruption Investigation Office for High-ranking Officials, which is prompting calls for better coordination among investigative agencies.

CIO, which requested a travel ban against President Yoon on Dec. 9, argues that it should oversee the investigation, since it would be a conflict of interest for the police to investigate cases in which police leaders including National Police Agency Commissioner Cho Ji-ho have been accused.

The same goes for the prosecutors since Justice Minister Park Sung-jae -- who has authority over the prosecution service -- attended the Cabinet meeting at the time of the declaration of emergency martial law. The 2017 case against Park was also headed by Yoon.

On Dec. 14, the CIO once again requested the prosecutors to transfer the related cases to them.

Amid a continuing war of nerves, some ironic situations unfolded when the prosecution took custody of former Defense Minister Kim while the police conducted searches of his office and seized evidence.

It is typical that the same investigative agency collects evidence and pressures the suspect for statements.