At a Los Angeles meeting held in a judge's chambers on Tuesday, Deputy Public Defender Derek Dillman said he had doubts over the mental competence of his client, 35-year-old Ivanna Lisette Ortiz of Orlando, Florida, court documents showed.
Ortiz has pleaded not guilty to firing at the house of Rihanna, her partner A$AP Rocky and their children while all of them were home.
Judge Shannon K Cooley ordered psychiatric evaluations and temporarily transferred the case to a Hollywood mental health court that specialises in determining whether defendants can understand the proceedings and go through a trial.
"It is the ethical obligation of counsel and the court to ensure that Ms Ortiz's rights are protected, including being able to assist counsel in conducting a defence in a rational manner," Dillman said in an email to The Associated Press.
If she is found incompetent, she could be held indefinitely in a state hospital until she is able to face the charges. She is set to appear on June 2 in the same courtroom where a judge recently found that a man accused of stalking Jennifer Aniston was incompetent to stand trial.
At a hearing a week earlier, Cooley had declined to pause the process for mental health evaluation, and Ortiz objected, saying she wanted the case to proceed on the path to trial.
She did not appear in court on Tuesday. Cooley ordered that she should continue to be held on nearly $US2 million ($A2.8 million) bail.
Police and prosecutors allege that on March 8, Ortiz pulled up in a Tesla to the Beverly Hills property of the singing superstar Rihanna and her rapper partner A$AP Rocky, pointed an AR-15 style rifle out the window and sprayed at least 20 bullets toward the property and a neighbouring house. No one was injured.
Shots hit an Airstream trailer that Rihanna and Rocky were inside, according to police interviews with the couple. Investigators found bullet holes in the trailer and on the exterior wall of the home's second-floor nursery, where the three kids were with their nanny.
Investigators said that after her arrest later that day, Ortiz told them "I wasn't attempting murder".
Ortiz is charged with 10 counts of assault with a semiautomatic firearm, one for each of the people on the two properties. She's also charged with three counts of shooting at an occupied vehicle or dwelling.
