Mexican environmentalist Gustavo Castro, the only witness to Berta Caceres' murder, launched an international criminal complaint against Honduras on Monday for detaining him in the country for weeks after the killing of a fellow activist.
Castro was a guest at Caceres' home in March 2016 when two gunmen shot and killed the high-profile Honduran activist who led an indigenous association fighting the construction of a hydroelectric dam in Honduras.
The suit was filed before the Inter-American Commission on Human Rights through Castro's lawyers, who said Honduras acted unconstitutionally and in violation of the activist's human rights.
The Mexican citizen, who was wounded in the attack, was detained by Honduran officials at the airport when he tried to return to his home country. He was taken to the Mexican embassy in the Honduran capital for weeks of questioning before being allowed to leave the country.
Both Caceres' family and Castro believe that the Honduran company Desarrollos Energeticos SA, better known as DESA, and the Honduran government contracted assassins to murder activists including Caceres. At least 120 environmental activists have been killed in Honduras since 2009, according to NGO Global Witness.
Caceres gained prominence for leading the indigenous Lenca people in a struggle against the Agua Zarca Dam, a controversial development project in the community of Rio Blanco that was put in motion without consent from local communities. Caceres suffered dozens of death threats and was reportedly on the top of a U.S.-backed military hit list leading up to her assassination.
Last year the United Nations Environment Programme posthumously awarded her its Champions of the Earth Prize for her "action and inspiration" so that "her death would not be in vain." Eight people have been arrested in relation to her murder.