The drug charges come after the unnamed 33-year-old woman claimed Green met her at a downtown L.A. nightspot in July 2012 and spiked her drink with
MDMA, the popular street drug known as "Molly." The woman said she later awoke naked in the singer's bed, with no recollection of how she got there.
After two rounds of investigations, however, prosecutors cited insufficient evidence to charge Green, born Thomas DeCarlo Callaway, with sexual assault.
Green, 39, has denied all wrongdoing and pleaded not guilty.
The charges are likely to tarnish the reputation of the cheerful pop musician, most recently seen as a judge on the hit
NBC singing-competition show "The Voice." His hits include the popular single "Forget You," and he recently reunited with his old group Goodie Mob for a new album.