The second phase of the BP oil spill trial that starts Monday could make a $7 billion difference for the British oil giant.
BP is fighting claims by the U.S. government and private lawyers that they were grossly negligent in the April 2010 oil spill, the largest offshore discharge in American history.
U.S. District Judge Carl Barbier will use the second phase of the trial to hear about BP's efforts to stop the flow of oil.
The plaintiffs say they will show how the company was unprepared for a spill in spite of documents indicating that it knew just how large and devastating a blowout could be. BP failed repeatedly in the months after the spill to shut off the flow, and it continued for 87 days until a capping device finally closed the discharge in mid-July 2010.
The most important fight of the second phase, however, will be over how much oil actually made it into the Gulf.
The government says it was 4.1 million barrels, based on analysis of subsea video and other scientific reviews that determined that 4.9 million barrels spewed out of the hole and 810,000 barrels were successfully collected by BP using tubes and other devices.
BP claims only 2.45 million barrels really made it into the waters, based on different assessments of the subterranean reservoir of oil and the oil that was successfully collected.
If the company is found grossly negligent, it would face a maximum pollution fine of $18 billion using the government's official total, but less than $11 billion based on BP's total.
The Clean Water Act penalties are capped at $1,100 per barrel spilled for simple negligence. However, gross negligence and willful misconduct by BP would increase the fines to $4,300 per barrel.
BP has already pleaded guilty to Obstruction of Congress for withholding data that showed more oil flowing than they initially admitted, although the former BP vice president charged with the same crime is fighting the charges.
Separately, an internal BP email from two days after the explosions showed company officials telling colleagues to keep quiet about a scientist's findings that oil was likely coming out of the well at a rate 15 times higher than what BP was telling the Coast Guard.
BP may actually find new life for their claims of a lower discharge by arguing that the oil flow actually got worse over the three-month spill. Videos of the blowout preventer clearly showed how the oil, gas and sediment tore through metal and rubber valves as it spewed out of the earth.
BP says that's why the government measurements, which took actual flow from the last days of the spill and assumed it was constant, are incorrect. Instead, BP said measurements of 57,000 barrels of oil a day in mid-July should have indicated that the spill was significantly smaller when it began.