Prosecutors suspect that Park took or solicited bribes worth 59.2 billion won ($51.9 million) from three local conglomerates -- Samsung, Lotte and SK -- for her or her friend.

Park's indictment was delayed as she was immune from prosecution until the Constitutional Court dismissed her as the country's president in a March 10 ruling.

"Merging the two cases is inappropriate as it can prejudice the judges against the defendant," attorney Lee Sang-chul said.

Her lawyers also pointed to the fact that Choi was indicted by a special prosecutor who was designated to look into the scandal, and Park was charged by state prosecutors. They claimed that the testimonies and evidence provided by the special prosecutor should not be used in Park's trial.

Still, it is unclear whether the court will accept Park's request.

"The two defendants' criminal allegations, as well as the list of witnesses, perfectly coincide with each other," the presiding Judge Kim Se-yun said during the session. "If we separate the cases, we need to summon the same witnesses twice."

Judge Kim also said there were precedents where a case filed by a special prosecutor was merged with a case filed by the prosecution. He said he will further review the request and make a decision.

Park was absent from Tuesday's session as her attendance was not mandatory.

The first formal hearing is slated for May 23. It will be the first public appearance made by the former leader, who has been jailed since March 31.

She is the country's third former president to stand trial over corruption allegations, after Chun Doo-hwan and Roh Tae-woo, who were convicted in the early 1990s. (Yonhap)