The duo, Alpha Lorenzo Walker and his girlfriend Tamara Eileen Diaz, have been jailed since their arrest on May 2. Both have pleaded not guilty and are scheduled to appear in court on May 16 for a hearing in which a judge will decide whether there is enough evidence for them to stand trial.

According to a felony complaint, Walker and Diaz attempted to obtain money from the Grammy-winning musician, who is identified by his birth name, Steveland Morris. An email message sent to Wonder’s studio was not immediately returned Friday.

Walker, 38, was on probation at the time of his arrest after pleading no contest to grand theft in May 2011. A judge issued a suspended three-year prison sentence in that case and he is due in court for a probation violation hearing May 31.

District attorney’s spokeswoman Jane Robison says Walker contacted Wonder’s representatives claiming to have embarrassing information about the musician. Detectives organized a sting and the pair were arrested. Police did not release additional details about their investigation Friday.

Walker identifies himself as Wonder’s nephew and is being held without bail because of another case.

Diaz’s bail is set at $95,000. Both are being represented by public defenders, who did not immediately return calls for comment.

Diaz was placed on three years of probation after pleading no contest in February 2011 to possession of marijuana with the intent to sell, court records show.

The case was first reported Friday by celebrity website TMZ.