The court is to decide whether the strong opposition party's congress in 2023 should be declared invalid. At the congress, the long-standing leader Kemal Kilicdaroglu was replaced by Özgür Özel.
If the court declares the election invalid, either Kilicdaroglu can return as leader, or the judges can appoint some form of temporary leadership for the party, according to the news agency AP.
CHP did well in the local elections in Turkey last year. Analysts in both Turkey and the outside world see the court process as a further sign that President Recep Tayyip Erdogan is afraid of the opposition's political strength, and is trying to neutralize CHP with fabricated charges.
Many CHP representatives are already being held after being accused of, among other things, corruption. The most well-known is Istanbul's mayor Ekrem Imamoglu, seen as a heavy potential challenger to Erdogan in the next presidential election.
As recently as Sunday, tens of thousands of Turks took to the streets and protested against the processes against CHP.
This government does not want democracy. They know they cannot win the election under democratic conditions, said Özgür Özel in a speech according to media in Ankara.
