HOUSTON, April 21 -- A U.S. federal court on Monday laid out a detailed schedule for the final phase of British oil giant BP' s civil trial over the 2010 Gulf of Mexico oil spill, setting the first day of the key chapter for Jan. 20, 2015, media reports said.

The penalty phase, during which U.S. District Judge Carl Barbier will listen to testimony from BP and government attorneys over the British oil company' s liabilities in the spill, will end around Feb. 5 next year, according to a court filing obtained by the Houston Chronicle.

The sprawling lawsuit has been ongoing for four years, but judges have not decided how much amount of fines BP should pay for the 2010 Deepwater Horizon rig explosion, which killed 11 people and triggered a massive oil spill into the Gulf of Mexico.

The trial's two previous phases dealt with causes of the disaster and the amount of oil that spewed into Gulf waters. Judges have not yet ruled on the amount spilled or on whether BP and others acted with gross negligence which led to the blowout.

BP and its partners could face fines up to 1,100 U.S. dollars per barrel of oil released under the penalty. If the parties are found not just negligent, but grossly so, fines could max out at 4,300 U.S. dollars per barrel. The U.S. government earlier estimated the total oil spill at 4.9 million barrels.

BP has so far paid more than 26 billion dollars in cleanup costs and damage claims to individuals, businesses and governments. It has estimated it will ultimately pay 42 billion dollars in oil spill costs.