According to court documents reported by Pitchfork, the 43-year-old initially pleaded not guilty to the charge in March 2020, but later altered his plea.
He is scheduled to be sentenced in January 2022.
The Beverley Hills Police Department first arrested Petty in November 2019 after learning he had move to California from New York and failed to submit his sex offender status in the process.
Petty is required to register as a sex offender after he was convicted of attempted rape in the first degree at the age of 16.
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