Government experts believe the oil was flowing from the well at a higher rate shortly after the blowout than it was when the well was sealed with a capping stack, which was equipped with a pressure gauge. BP's experts concluded that flow rates increased over time, due in part to the erosion of steel rams on the rig's blowout preventer.
For the first phase, lawyers for Gulf Coast residents and businesses and for the Gulf states were adversaries with Deepwater Horizon owner Transocean Ltd. and cement contractor Halliburton. But they are aligned against BP and Anadarko Petroleum Corp., a minority owner of the Macondo well, for the second phase.
Barbier ultimately could decide how much more money BP and its contractors owe for their roles in the deadly disaster. A "penalty phase" for the trial has not been scheduled yet.
Transocean and Halliburton argue that their share of responsibility should be reduced as a result of BP's alleged misconduct in planning for and responding to the spill.
In May 2010, BP tried in vain to use the "top kill" method to stop the flow of oil by pumping mud and other material into the blowout preventer. Plaintiffs' lawyers claim BP knew the strategy was doomed to fail based on higher flow rate estimates that the company didn't share with federal officials at the time.
"These lies and omissions delayed the capping of the well," they wrote.
A capping stack ultimately sealed the well on July 15, 2010. BP said the device was specifically built for the "unique challenges" of the Macondo blowout.
"Neither (federal) regulations nor industry standards required a capping device when responding to a deep-water blowout, and no deep-water blowout had been secured with such a device previously," company attorneys wrote.