Amanda Bynes could face a year in jail over two hit and run charges.

The 'Hairspray' actress will answer to counts of fleeing the scene of two crashes - one in April and another last month - when she appears in court for arraignment on September 27.

The 26-year-old initially avoided prosecution over the first smash on the Los Angeles Freeway on April 10 due to the absence of an independent witness.

However, the case was re-opened after the second incident August 4.

Los Angeles City attorney's spokesman Frank Mateljan is bringing the charges against Amanda after dents on her black BMW car appear to match those of a damaged Volvo, which was rear ended.

A witness had subsequently reported seeing Amanda leaving the scene without giving her information following the incident.

Each of the two misdemeanours carries a maximum sentence of six months prison.

Amanda was also charged with Driving Under The Influence (DUI) in June after allegedly scraping a police patrol car while attempting a turn in her BMW on April 6 and being arrested.

She later appealed to US President Barack Obama for help on Twitter, writing: ''Hey @BarackObama... I don't drink. Please fire the cop who arrested me. I also don't hit and run. The end.''