As TMZ first reported, Bynes allegedly rear-ended a BMW, and fled the scene while driving a rental on the 101 Freeway. The L.A. City Attorney's Office rejected the case because there was no independent witness to finger Amanda as the suspect.
Law enforcement sources tell us that all changed when Bynes was accused, yet again, of hit-and-run on August 4.
We're told prosecutors have decided to re-open the April incident -- which means Amanda could end up with 2 misdemeanor hit-and-runs ... with each carrying a max sentence of 6 months.
Don't forget, Bynes also has a DUI on her plate from a whole other incident. She pled not guilty to that one back in June.