The team looking into whether former President Yoon Suk Yeol intervened in a 2023 Marine death probe has wrapped up its investigation.

Special prosecutor Lee Myeong-hyeon said during Friday's final briefing that every member of his team had carried out the investigation with a resolve to leave no room for doubt and that the group had revealed the substantive truth behind most of its assigned cases.

During its 150-day operation, the team conducted approximately 180 search-and-seizure operations at the presidential office, the defense ministry and the justice ministry and questioned approximately 300 suspects and witnesses.

Thirty-three people were indicted in the case, including the former president, who was charged with meddling in the initial military inquest to exclude former Marine Corps First Division Commander Lim Seong-geun from a list of suspects.

Yoon also faces charges of failing to uphold procedural legitimacy when naming then-Defense Minister Lee Jong-sup as ambassador to Australia to help him leave the country and dodge questioning.

The team handed Lim charges of occupational and gross negligence, causing death.

Investigators, however, failed to substantiate claims that associates had lobbied to exclude Lim from the military's initial list of suspects.

The team also plans to refer to the National Office of Investigation allegations that the Yoon administration exercised undue influence after military case files were sent to the civilian police.

A year after receiving the files, the Gyeongbuk Provincial Police decided not to refer Lim to trial.