District attorney's spokeswoman Jane Robison says Alpha L. Walker and Tamara Diaz entered the pleas Thursday and will return to court in the future for a pretrial hearing.
It was the pair's first court appearance since a judge determined there was enough evidence for them to stand trial earlier this month.
Walker is Wonder's cousin and is accused of trying to extort the Grammy-winning musician over a video that portrays Wonder negatively. Walker and Diaz, his girlfriend, were arrested in May after receiving $10,000 from Wonder's attorney in a police sting.
Walker's attorney says his client simply made a movie about his life and his actions are protected by the First Amendment.
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