The DTP warns a ban will risk inflaming the Kurdish insurgency
Turkey's Constitutional Court is considering whether to ban the country's leading Kurdish party.
Prosecutors accuse the Democratic Society Party (DTP), which holds 21 seats in the 550-member parliament, of supporting Kurdish separatist rebels.
The 11 judges are expected to take days or weeks to reach their verdict.
Tension in the mainly Kurdish south-east of Turkey has risen in recent months despite a government drive to improve ties with the Kurdish minority.
Analysts say if the court decides to close down the DTP, it could derail Prime Minister Recep Tayyip Erdogan's effort to broaden the rights of Kurdish citizens.
Several predecessors of the DTP have been shut down in the past over links to the separatist PKK, which is outlawed and classed by the US and EU as a terrorist group. But the party's members have reformed under different names.
Some 40,000 people have died since the PKK launched its armed campaign in 1984. The government's recent Kurdish initiative is aimed at ending the insurgency.
When eight PKK members handed themselves in at the Turkish border in October, the government and many nationalists were angry that there was a large gathering offering a hero's welcome, reportedly organised by the DTP.
One of the party's leaders, Emine Ayna, warned that banning the DTP would damage attempts to end the Kurdish conflict.
It "would lead to a much worse climate than the one in the 80s and 90s" when the PKK insurgency began and reached its peak, she said.