"BP repeatedly chose speed over safety," Roy said, quoting from a report by an expert who may testify.
Roy said the spill also resulted from Transocean's "woeful" safety culture and failure to properly train its crew. And Roy said Halliburton provided BP with a product that was "poorly designed, not properly tested and was unstable."
Brad Brian, a lawyer for Transocean, said the company had an experienced, well-trained crew on the rig. He said the Transocean workers' worst mistake may have been placing too much trust in the BP supervisors on the rig.
"And they paid for that trust with their lives," Brian said. "They died not because they weren't trained properly. They died because critical information was withheld from them."
A lawyer for Halliburton defended the company's work and tried to pin the blame on BP and Transocean.
"If BP had shut in the well, we would not be here today," Halliburton's Donald Godwin said.
Underhill, the Justice Department attorney, heaped blame on BP for cost-cutting decisions made in the months and weeks leading up the disaster. He said two BP rig supervisors, Robert Kaluza and Donald Vidrine, disregarded abnormally high pressure readings that should have been glaring indications of trouble.
Kaluza and Vidrine have been indicted on federal manslaughter charges.
Brock, the BP lawyer, said Transocean employees on the rig also played roles in misinterpreting the "negative pressure test."
"It was a mistake made by several men from two different companies," Brock said. "They were trying to get it right. They were trying to do the right thing."
Hundreds of attorneys have worked on the case, generating roughly 90 million pages of documents, logging nearly 9,000 docket entries and taking more than 300 depositions from witnesses who could testify at trial.
"In terms of sheer dollar amounts and public attention, this is one of the most complex and massive disputes ever faced by the courts," said Fordham University law professor Howard Erichson, an expert in complex litigation.
The spill fouled marshes, killed wildlife and closed fishing grounds. Scientists warn that the disaster's full effect may not be known for years. But they have reported dying coral reefs and fish afflicted with lesions and illnesses that might be oil-related.