BP Plc fostered a culture that put cost-cutting over safety before the 2010 Gulf of Mexico oil spill, a forensic engineer said in the first day of testimony in the federal civil trial centred on the disaster.
"There is ample evidence of intense pressure within the system," said Bob Bea, co-founder of the Center for Catastrophic Risk Management at the University of California, Berkeley.
"With stress and pressure come sacrifices to safety."
Mr Bea was the first witness for the plaintiffs, the US Justice Department and US Gulf Coast states suing well owner BP, rig owner Transocean Ltd and well cement provider Halliburton Co.
The plaintiffs plan to call Lamar McKay, chairman and president of BP America, to testify as a hostile witness once Bea wraps up.
Mr McKay is a member of the London-based oil company's executive committee, alongside Chief Executive Officer Bob Dudley.
Mr Bea consulted with the White House commission that investigated the spill and prepared a report faulting BP for the plaintiffs in the case.
He also had consulted with BP on risk management prior to 2005.
He said BP cut its Gulf of Mexico costs by 22% from 2008 to 2009 while increasing oil and gas output by 55%.
Mr Bea said during questioning by Robert Cunningham, a lawyer for the plaintiffs, that he had told BP that "money isn't everything" and that incentives for major accident prevention should be on equal footing with incentives for profits.
"It's a culture of every dollar counts," Mr Bea said.
He had yet to be cross-examined by BP lawyer Mike Brock.
The April 2010 blowout caused an explosion that killed 11 men, sank a rig and spewed more than 4 million barrels of crude oil into the Gulf.
Well-known in New Orleans, the site of the trial, Mr Bea was a key witness in litigation over failed levees when Hurricane Katrina hit in 2005, flooding much of the city and leaving more than 1,800 people dead.
The nonjury trial before US.District Judge Carl Barbier is split into three phases, with the first focused on allocating blame among the defendants and the severity of their negligence.