SEOUL (REUTERS) - The outgoing chief judge of South Korea's Constitutional Court urged the court on Wednesday (Jan 25) to conclude the impeachment trial of President Park Geun Hye by March 13, when the retirement of another judge will reduce the nine-judge bench to seven.

Ms Park was impeached amid a corruption scandal that has engulfed her administration over recent months. If the impeachment is upheld, she will become the first democratically elected leader to be removed from office.

Chief Judge Park Han Chul, who retires on Jan 31, said on the ninth day of the impeachment hearing that the retirement of two judges may distort the court's impartiality.

"If another judge's seat is vacated, that is not just a matter of one vacated seat but could distort the outcome of the decision," he told a public hearing.

The court has previously stressed the need to balance a speedy resolution of the crisis with proper legal deliberation, but this was the first time the court has mentioned a specific timeline.

Ms Park was impeached by parliament in December after accusations that she colluded with long-time friend Choi Soon Sil to pressure big businesses to donate to two foundations set up to back the president's policy initiatives.

Ms Park, 64, remains in office but has been stripped of her powers while she awaits her fate.

Both the president and Choi have both denied wrongdoing.

If she has to stand down, her successor must be elected within 60 days.

The nine-judge court will be reduced to seven on March 13, when Judge Lee Jung Mi is set to retire.

Seven sitting judges are the minimum required by law to rule on an impeachment, with six needed to vote one way or the other for the decision to be valid.

Sources with intimate knowledge of the court's inner workings told Reuters that seven judges, for a landmark ruling such as this, was too few and could invite questions of the ruling's legitimacy, especially if the ruling is not unanimous.

The sources declined to be identified due to the sensitivity of the matter.