Brock said Transocean's crew members ultimately were responsible for well control on the rig and didn't need permission from BP supervisors to shut in the well.
"Shut in the well, then seek advice," he 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.
The 2010 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.