The civil trial for one of the largest accidental oil spills in history began Monday before Judge Carl Barbier at New Orleans federal court.
To avoid additional fines, BP's lawyers must prove the company is not guilty of "gross negligence". A conviction could result in penalties as high as $17.6 billion, an all-time record.
This would be on top of the $4.5 billion BP has already paid out, along with the $37 billion it has committed to clean-up and restoration efforts.
The 87-day oil spill is considered to be one of the largest in U.S. history. Eleven people died and more than 4 million barrels of oil were spilled into the Gulf of Mexico between April 20 and July 15, 2010, causing extensive damage to bird sanctuaries, marine and wildlife habitats.
Massive losses were also reported in the fishing and tourism industries.
With files from Reuters