SEOUL (THE KOREA HERALD/ASIA NEWS NETWORK) - Like all other criminal cases, conclusive judgement on the case of former Chief Justice Yang Sung-tae should be given only after the final court verdict.

Nevertheless, even at this stage, the case has exposed dark sides of Korean society.

Yang, who was taken into custody last week, is the first former chief justice to face criminal indictment for something he had done while in office.

That the court issued an arrest warrant for Yang as requested by prosecutors highlights the gravity of what happened while he was head of the judiciary branch.

Prior to Yang's arrest, both former President Lee Myung-bak, who appointed Yang as chief justice in 2011, and his successor, Park Geun-hye, who was impeached, had already been put behind bars on charges of corruption and abuse of power.

That the three are now wearing prison garb is a poignant reminder of problems surrounding the highest echelon of the nation's governing system.

The arrest of Yang came as a shock, as it belied public perception that the judiciary branch would be relatively free from wrongdoings and misconduct than the executive and legislative branches.

Those with knowledge of Korean politics cannot argue that the state prosecution's investigation into the case has nothing to do with the current Moon Jae-in government's purge of the past conservative governments that had been led by Lee and Park.

This, however, should not discredit the findings made by the prosecution so far in its investigation of about 100 incumbent and former judges for about seven months, which resulted in the arrests of Yang and his former top aide Im Jong-heon, former deputy director of the National Court Administration.

The charges raised by prosecutors against Yang and Im showed how vulnerable the Korean court and its justice system were to external and internal interferences.

For instance, prosecutors charged that Yang and Im conspired with the Park administration to delay a Supreme Court ruling on a damages suit filed by Korean victims of forced labour during the Japanese colonial period.

The Park administration had sought a delay in the ruling because a verdict in favour of the Korean victims would affect relations with Japan.

In return, the Supreme Court under Yang wanted Park to support its plan to establish a new court of appeals, which would relieve the Supreme Court's burden.

There are more cases indicating the possibility that Yang and his aides intervened in court rulings.

In other words, those who should have protected the independence of judges did the opposite, threatening the justice system and the rule of law.

It is a flagrant violation of the Constitution, which stipulates that "judges shall rule independently according to their conscience and in conformity with the Constitution and Act."

There are other ongoing cases of alleged intervention in trials by outside figures.

One such latest case involves Rep. Seo Kyung-kyo of the ruling Democratic Party of Korea, who allegedly met a judge who acts as a liaison officer between the court and the National Assembly to seek a favour in a trial involving the son of her acquaintance.

Several other lawmakers were implicated in similar cases.

Getting to the bottom of these cases is one of the first tasks the prosecution and the court should tackle to reform the justice system and restore public confidence in the judiciary.

The case involving Yang and the allegations involving lawmakers are certain to prompt demands for retrials of past cases.

There may be some that must be redressed, as in the cases of undue verdicts given to pro-democracy activists during military dictatorships.

But accepting all demands for reviews of past cases could shake the foundation of the court system.

Ideologically sensitive cases, like rulings on far-left politicians and the outlawing of a teachers' union, could further exacerbate deep animosity between conservatives and progressives.

Prudence is required from everyone - politicians, judges, the public and not least incumbent Chief Justice Kim Myeong-su - to help the judiciary overcome the crisis and rebuild without jeopardising the foundation of the court system.

The Korea Herald is a member of The Straits Times media partner Asia News Network, an alliance of 23 news media organisations.