Prosecutors urged a federal appeals court panel on Wednesday to reinstate a criminal charge alleging that a former BP executive obstructed a congressional investigation into the 2010 oil spill in the Gulf of Mexico.
The case before the 5th US Circuit Court of Appeals involves allegations that David Rainey failed to disclose information from BP indicating that the amount of oil gushing into the Gulf after the Deepwater Horizon explosion could have been far higher than estimates then being made publicly.
Last year, US District Judge Kurt Engelhardt threw out the obstruction-of-Congress charge against Rainey.
At issue is whether the law Rainey is accused of breaking applied to congressional subcommittee investigations.
Arguments centred on legal semantics during the hearing conducted before the appeals court judges - Emilio Garza, E. Grady Jolly and Stephen Higginson.
Engelhardt had ruled in favour of defence lawyers who argued that the law refers specifically to committees, but not subcommittees.
Justice Department attorney Christopher Smith, arguing for reversal of Engelhardt's ruling, said the appeals court should use a broad definition of the word "committee" in interpreting the law.
Arguing for the defence, Reid Weingarten told the panel that the term "committee" in Congress is a narrowly defined legal term.
"If you read the statute, you don't see 'subcommittee' anywhere, end of story," he said.
Engelhardt had also sided with defence attorneys who said prosecutors failed to expressly allege that Rainey knew of the pending congressional investigation he was accused of obstructing.
Prosecutors say in briefs that the allegations are clear in the indictment.
The panel gave no indication when it would rule.
Prosecutors allege that Rainey during a May 4, 2010, congressional briefing failed to disclose information about the estimated rate that oil was spewing from BP's blown-out Macondo well after the April rig explosion.
They also claim Rainey responded to a letter from a subcommittee chairman, then-Rep. Edward Markey, with false and misleading information about flow-rate estimates.
Markey is now a Democratic senator from Massachusetts.
Weingarten has characterised the obstruction charge thrown out by Engelhardt as central to the government's case against Rainey, who has pleaded not guilty.
Still, even if the appeals court upholds the dismissal, Rainey faces a charge of lying to law enforcement agents. And prosecutors also have obtained a new, re-worded indictment on the obstruction charge.
Rainey's trial has been postponed indefinitely pending the appeal.
The explosion on the BP-operated drilling rig Deepwater Horizon four years ago killed 11 workers about 50 miles (80 kms) off the Louisiana coast and set off the nation's worst offshore oil disaster.
A former BP engineer, Kurt Mix, has been convicted and is seeking a new trial on a charge that he obstructed the investigation by deleting text messages to and from a supervisor.
BP well site leaders Robert Kaluza and Donald Vidrine have pleaded not guilty to manslaughter charges stemming from the 11 deaths.
Anthony Badalamenti, a former manager for Halliburton Energy Services, BP's cement contractor on the rig, was sentenced to one year of probation for destroying evidence in the aftermath of the spill.