The Ministry of Internal Affairs has accused Yunus of "insulting" the ministry and causing "moral damage" to the reputation of the police after giving an interview in which she questioned the conduct of a kidnapping trial in which a defendant had alleged police involvement.
Yunus' trial is scheduled to begin in Baku on January 23.
In a statement, Rachel Denber, director of HRW's Europe and Central Asia division, said "a judgment against Yunus would set a terrible precedent for freedom of expression in Azerbaijan."
"When allegations are made of official involvement in kidnapping, the public has an interest in knowing what has been done to investigate," said Denber. "The Azerbaijani government should focus on ensuring that justice is done instead of targeting activists for their legitimate criticism."
Activists and media watchdog groups say the Yunus case is but one more example of the Azerbaijani government cracking down on free expression.
On January 1, the government banned foreign radio on local frequencies, a move that ended the broadcasts of RFE/RL, the BBC, and Voice of America.