The badly mutilated corpse of Arsene Salomon Mbani Zogo, known as "Martinez," was found a few days after his abduction in front of a police station outside the capital Yaounde on January 17, 2023.
The 50-year-old radio reporter was an outspoken critic of alleged corruption and cronyism in the Central African nation, often singling out government officials by name.
International NGOs say the regime of President Paul Biya, 91, who has ruled with an iron fist for more than 41 years, routinely curtails opposition.
No trial date has yet been set for the suspects, who include Jean-Pierre Amougou Belinga, an influential businessman and owner of Anecdote media group, who was arrested two weeks after Martinez's murder.
"He has been ordered to stand trial on a fabricated charge — complicity in torture," Belinga's lawyer Charles Tchoungang told AFP.
The court order said "sufficient charges against the indicted" justified ending the judicial enquiry and setting a trial.
Maxime Leopold Eko Eko, former head of Cameroon's DGRE spy agency, must also stand trial on charges of complicity in torture, the order added.
The DGRE's operations director, Justin Danwe, faces charges of complicity in murder.
But many Cameroonians fear justice may never be done in a country ranked by Reporters Without Borders as 118th out of 180 for press freedom.
After both Belinga and Eko Eko were freed from detention without formal explanation in December, a new investigative judge — the third — was named to handle the case.
Rights group, Human Rights Watch, says freedom of expression continues to be restricted in Cameroon, noting that three independent journalists were killed there last year.