"I will go to the trial with my head held high. No one better than us can speak of our struggles and what we have suffered," Zuñiga added.
Castillo is the director of Energy Development (DESA) company, which planned to build a hydroelectric reservoir in the Gualcarque River, a place which is sacred to the Lenca people.
Berta Caceres opposed the hydroelectric project claiming it would cause damage to the environment. Before she got killed, she received death threats for defending the river and the rights of the Lenca people.
The accused allegedly hired a group of hitmen to assassinate Berta in her house in the La Esperanza community, Intibuca Department, on March 2, 2016.