The Constitutional Court on Tuesday opened the 11th hearing of President Park Geun-hye's impeachment trial as uncertainties persisted over when and how the ruling will be delivered.

Two witnesses were scheduled to testify to help the justices determine the legitimacy of Park's impeachment. The third witness Kim Ki-choon, a former presidential chief of staff seen as a key witness in the trial, submitted a statement to the court Monday to indicate his planned absence. He cited health issues.

Jeong Hyun-sik was the first to testify on allegations Park's friend Choi Soon-sil extorted donations from conglomerates to the nonprofit K-Sports Foundation, which she allegedly controlled and where he worked as the secretary-general.

Park has been named an accomplice in the suspected crime.

"Without naming Choi Soon-sil, I once asked senior presidential secretary An (Chong-bum) if he could verify whether this woman who was giving guidelines (for the foundation's operation) shared the same intentions as the executive (the president)," Jeong recalled, noting that Choi had no official title but oversaw everything from hiring and assigning work to salary-setting.

Jeong claimed An, a former senior secretary for economic affairs and then for policy coordination, was deeply involved in the foundation's work, which led him to believe An was acting on the president's orders.

Later in the day, former Culture Minister Kim Jong-deok is scheduled to appear for questioning on allegations Park forced the resignations of senior ministry officials for their noncooperation in the execution of a supposed blacklist of artists critical of the conservative administration.

The court is also set to decide whether to accept or reject Park's request to summon an additional 15 to 17 witnesses to future hearings.