SEOUL (REUTERS) - The woman at the centre of a corruption scandal gripping South Korea angrily protested her innocence on Wednesday (Jan 25), shouting that she had been made to confess as she was forcibly summoned for questioning.

Choi Soon Sil, who has been indicted for meddling in state affairs through her friendship with impeached President Park Geun Hye, made the protest at the special prosecutor's office, before being pushed into an elevator by correctional officers.

The dramatic scenes came as the outgoing chief judge of the Constitutional Court urged the bench to wrap up Ms Park's impeachment trial by March 13, when the retirement of another judge will reduce the nine-judge court to seven and could raise questions about the verdict.

His comments were the clearest indication of the timing of a decision on Ms Park, either to remove her from office with an election to be called 60 days later, or for her to be reinstated.

Ms Park was impeached amid the influence-peddling 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.

Ms Park, 64, was impeached by parliament in December after accusations that she colluded with Choi to pressure big businesses, including Samsung, to donate to two foundations set up to back the president's policy initiatives. She remains in office but has been stripped of her powers while she awaits her fate.

Ms Park, Choi and Samsung have all denied wrongdoing.

Choi was brought into the special prosecutor's office on an arrest warrant after refusing to answer several summons for questioning.

"I am being forced to confess committing crimes jointly with the president," she shouted to reporters. "I don't deserve to be treated like this. And my baby and my grandson," she said as guards pushed her into the elevator.

As part of their investigation, prosecutors are looking into Samsung Group's sponsorship of the equestrian riding career of Choi's daughter Chung Yoo Ra, 20, who was arrested in Denmark after being sought by South Korean authorities.

Ms Chung has been accused of criminal interference related to her academic record and other unspecified charges.

JUDGES' RETIREMENTS ADD UNCERTAINTY

Chief Judge Park Han Chul, who retires on Jan 31, urged the court on Wednesday to conclude the impeachment trial by March 13, when the retirement of another judge will reduce the Constitutional Court's nine-judge bench to seven.

Speaking on the ninth day of the impeachment hearing, the chief judge said the retirement of two judges may distort the impartiality of the court.

"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.

Seven sitting judges are the minimum required by law to rule on an impeachment, with six needed to vote to uphold the motion for Ms Park to be removed.

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.