The trial of a businessman accused of being the "intellectual author" of the 2016 murder of high-profile Honduran environmentalist Berta Caceres has begun in the capital Tegucigalpa.

David Castillo was president of electric group Desarrollos Energeticos (DESA), the company behind a hydroelectric dam that at the time of her death Caceres was mobilising opposition against.

A coordinator for indigenous organizations in Honduras, Caceres was assassinated in March 2016 by gunmen who entered her house in the community of La Esperanza.

The trial of David Castillo, accused of being the "intellectual author" of environmentalist Berta Caceres' murder, has begun
The trial of David Castillo, accused of being the "intellectual author" of environmentalist Berta Caceres' murder, has begun AFP / Orlando SIERRA

Her murder brought international attention to the threats and intimidation faced by environmentalists and rights activists in the Central American nation.

"There is overwhelming proof against David Castillo and he should be convicted," Caceres' daughter Berta Zuniga told AFP at an indigenous religious ceremony organised in front of the court where the trial opened Tuesday.

"Berta (Caceres) did not die, she multiplied", shouted around a hundred people, in front of an altar with candles, flowers and photos of the environmentalist.

Castillo, a former military officer who trained at the US academy West Point, was arrested in March 2018.

An indigenous religious service took place outside the court
An indigenous religious service took place outside the court AFP / Orlando SIERRA

He was accused of masterminding her murder, in connection with which other DESA employees have already been convicted.

The hydroelectric dam was planned to sit across the Gualcarque River, on which indigenous communities depended -- and protests organised by Caceres and her organisation COPINH had paralyzed the construction site.

In 2019 Sergio Rodriguez, a top DESA official, was jailed for 30 years for orchestrating the killing with Douglas Bustillo, DESA's former chief of security, and soldier Mariano Diaz.

The court found they paid four gunmen $4,000 to carry out the murder.

"As president of DESA, David Castillo hired Douglas Bustillo, who hired the contract killers," Caceres' daughter Zuniga said. "There is evidence in their communications."

Zuniga added that DESA's partners, particularly bankers, should also be held accountable.

The killing sparked international outrage, with the United States and the European Union both demanding Caceres' killers be brought to justice.

After Castillo's pre-trial hearing in October last year, rights group Amnesty International issued a statement reminding the Honduran authorities "to comply with due process", after a broadcast of the hearing could not be accessed remotely, "thus limiting publicity and the transparency of the judicial process."