Singer Rihanna will appear at a hearing next month as a possible witness in the assault case against ex-boyfriend Chris Brown, her lawyer has said. Donald Etra said prosecutors will order the star to appear at the 22 June hearing, which will assess if there is enough evidence to go to trial. The 20-year-old was charged with assault and making criminal threats in March after a row with his girlfriend. The pop star has pleaded not guilty to the charges. "Rihanna has always agreed to do whatever the law requires her to do," Etra said. "She is totally willing to testify if called to do so." Defence hinge The hearing will mark Rihanna's first appearance in court since charges were filed following the February incident. If she is called to testify, the 21-year-old would be subject to cross-examination by Brown's lawyer, Mark Geragos. Meanwhile, a judge on Thursday rejected a motion by Geragos to receive police and investigative records related to the case, and the apparent leak of a photo of a beaten and bruised Rihanna. The lawyer revealed last month that his defence would hinge on the impropriety of the Los Angeles police force, which he says purposely leaked the image to gossip website TMZ. But Los Angeles Superior Court Judge Patricia Schnegg called the motion "a fishing expedition" and told Geragos the request was premature and he could file it again after the preliminary hearing. Geragos said he still plans on filing a motion to dismiss the case, but said he will do so only after the initial court hearing. Brown faces up to four years in prison if convicted. Source: BBC