Prosecutors have arrested a former defence minister over an incident in which a South Korean civil servant was killed by North Korea near the two countries’ disputed sea boundary in 2020.

The focus now is on whether the investigation will be widened to implicate Moon and other key members of his administration.

Two more probes are underway that could lead to criminal charges against senior opposition lawmakers.

The legal inquiries are sending shock waves through the liberal opposition camp, which is locked in a bitter fight with the government of conservative President Yoon Suk-yeol.

The trouble began on Sept 21, 2020, when a 47-year-old fisheries official went missing from a government ship near Yeonpyeong Island.

North Korean military personnel discovered the official adrift at sea and shot him the next day.

No one has explained how the official, who was in charge of providing instructions for fishing operations, disappeared from the ship.

Moon’s government made no serious attempt at a rescue, regarding the official as a defector to the North.

But South Korea’s coast guard announced in June this year that there was little evidence the slain official had been trying to escape to the North, reversing its earlier conclusion.

In South Korea, it is illegal to defect to the North.

The question of whether the official was actually trying to defect or fell overboard is very important to the honour of his family and that of the man himself.

Many pundits say the Moon administration should have dealt with the case more thoroughly.

Prosecutors suspect Moon’s leadership team steered the case to match its official version of the incident.

In a report on the killing published in October, the board of audit and inspection, a state watchdog, said that the defence ministry initially believed the official fell overboard, but that the presidential office ordered the ministry and coast guard to treat the incident as a failed defection attempt.

On Oct 22, prosecutors arrested former defence minister Suh Wook for alleged abuse of power and forgery of an official document.

Suh is accused of ordering parts of intelligence reports erased to conceal facts about the killing of the fisheries official, including a section about North Korean military communications intercepted by the South Korean military.

In an Oct 27 news conference, former senior Moon administration officials, including the director of his national security office, Suh Hoon, criticised the investigation, saying, “We never tried to baselessly push a defection angle, nor ordered the deletion of data.”

Prosecutors are planning to question Suh and other former Moon officials over the case, according to Dong-A Ilbo, a conservative daily.

The newspaper also reported that Moon could be a target of the investigation.

The incident occurred at an inconvenient time for the former president’s administration.

At that time, its effort at reconciliation with the North had stalled diplomatically.

Moon was also about to give a speech by video to the UN General Assembly calling for a formal declaration of an end to the 1950-1953 Korean War as part of his effort to shore up the diplomatic push.

Prosecutors are also accelerating their examination of the 2019 repatriation of two North Korean fishermen.

In November 2019, the fishermen were sent back to the North five days after they were captured by the South Korean navy, despite saying they wanted to defect.

The two told South Korean interrogators that they had fled after the killing of 16 of their fellow crew members.

The two were executed after their repatriation, according to South Korean media.

One former prosecutor sees the case as a violation of South Korea’s constitution, which treats residents of North Korea as potential South Korean citizens.

As the two expressed a desire for asylum, the case should have been handled in line with South Korean law, said legal experts.

The Moon administration, however, did not investigate the alleged killing of the crew members, concluding instead that the two fishermen were criminals who did not qualify as refugees under international law.

The incident occurred soon after working-level talks between the US and North Korea had collapsed, dealing a serious blow to Moon’s North Korea policy.

On Oct 19, prosecutors summoned Noh Young-min, Yoon’s former presidential chief of staff, for questioning.

Noh presided over a meeting where the decision to repatriate the fishermen was made.

Prosecutors are seeking to clarify how the decision was made and by whom.

Separately, prosecutors are investigating opposition leader Lee Jae-myung in connection with an urban development project he pursued as mayor of Seongnam, southeast of Seoul.

Prosecutors recently arrested a close aide to Lee, now chairman of the Democratic Party, for allegedly taking 800 million won in bribes from a private investor linked to the project.

They also searched the party’s headquarters.

Prosecutors believe some of the money was used to finance Lee’s unsuccessful presidential campaign.

If Lee is convicted of violating the election law, he is unlikely to be a presidential candidate again.

Lee has categorically denied the allegations against him, accusing prosecutors and the Yoon administration of political persecution.

A progressive civic group that supports the opposition party on Oct 22 staged a rally in central Seoul calling for Yoon’s resignation.

The parliament, meanwhile, has been gripped by an all-out partisan battle, with the opposition bloc boycotting Yoon’s policy speech on Oct 25.

It is by no means unprecedented for South Korean prosecutors to target opposition leaders.

During the Moon administration, two conservative former presidents, Lee Myung-bak and Park Geun-hye, were indicted on bribery and other charges, and sentenced to prison.

There is a heated debate in the country over whether law enforcement authorities have too much leeway to engage in politically fraught investigations.

Questions have been raised over whether the three cases now under investigation are really about legal violations by powerful politicians, or a vendetta by those in power against political foes.

The answers to those questions will have to wait until the courts render their verdicts.