A US jury is deciding whether a former BP engineer broke the law or harmlessly swiped his finger across a mobile phone when he deleted hundreds of text messages in the aftermath of the deadly Gulf of Mexico oil spill.
Jurors met in New Orleans for about an hour and a half before asking to go home for the night. They will resume deliberations today.
Prosecutors say Kurt Mix, 52, was trying to destroy evidence of the 2010 Deepwater Horizon blow-out when he deleted two strings of text messages - one with a supervisor and another with a BP contractor.
"It's a crime and Kurt Mix should be held accountable," US Justice Department prosecutor Leo Tsao said in his closing arguments.
But defence lawyer Michael McGovern said the charges against Mix were "unfair and baseless" and the product of investigators' "rank incompetence". He described Mix as a brilliant engineer who worked tirelessly to seal the blown-out well and "doesn't have a corrupt bone in his body".
"You did not hear one bad word about Kurt Mix. Not a single one," he told the jury. "Not one bad word about Kurt's character. Not one bad word about Kurt's work."
Mix did not give evidence at his two-week-long trial, where he is charged with two counts of obstruction of justice. Each count carries a maximum sentence of 20 years in prison and a 250,000-dollar (£153,000) fine.
Mix was one of four current or former BP employees charged with crimes related to the spill. His case was the first to be tried.
The April 20 2010 blow-out of BP's Macondo well off the coast of Louisiana triggered an explosion that killed 11 workers on the Deepwater Horizon drilling rig and spawned America's worst offshore oil spill. Millions of gallons spewed into the Gulf, killing wildlife, polluting marshes and staining beaches while the company scrambled for weeks to seal the well.
Mix was on a team of experts who tried in vain to stop the flow of oil using a technique called "top kill". He had access to internal data about how much crude was flowing from the blown-out well.
On May 26, the day that top kill began, Mix estimated in a text to a supervisor that more than 630,000 gallons of oil a day were spilling - three times BP's public estimate of 210,000 gallons daily and a rate far greater than what top kill could handle.
That text was in a string of messages that Mix exchanged with his supervisor, Jonathan Sprague, before deleting it in October 2010. Investigators could not recover 17 of the messages in the string.
Mr Tsao said Mix had a "powerful motive" for deleting that string of messages. It confirmed his own personal belief that top kill was failing because the flow rate was too high. The flow rate during top kill was an "absolutely crucial" issue for the US government investigation of the spill, Mr Tsao added.
"Criminal investigations simply cannot work if people are allowed to do what Kurt Mix did," he said.
But Mr McGovern said Mix's flow-rate estimates were shared with a host of government agencies. "What kind of hiding is that?" he asked.
Mix also deleted a string of text messages that he exchanged with BP contractor Wilson Arabie in August 2011, several weeks after federal authorities issued a subpoena to BP for copies of Mix's correspondence. The same count that charges Mix with intentionally deleting those messages also says Mix deleted a voicemail from Mr Arabie and a voicemail from Mr Sprague.
Mr McGovern said Mix preserved plenty of evidence, including emails on his BP laptop, which he said shows there wasn't anything insidious about his deletion of the texts. Investigators chose to ignore that evidence, Mr McGovern added. "We were the ones who had to show you the truth," he said.
The lawyer suggested that Mix could have accidentally deleted the entire string of messages with Mr Sprague when he only intended to erase two photos of himself from the bottom of the string. Mr Tsao, however, said it defies logic that Mix accidentally deleted messages because he was confused about how the phone worked.
"Kurt Mix is a smart guy," Mr Tsao said. "He knows how to use his iPhone."
The three other current or former BP employees who've been indicted on spill-related criminal charges await trials.
BP well site leaders Robert Kaluza and Donald Vidrine have pleaded not guilty to manslaughter charges over the rig workers' deaths. Prosecutors say they botched a key safety test and disregarded abnormally high pressure readings that were glaring signs of trouble before the blow-out.
Former BP executive David Rainey is charged with concealing information from Congress about the amount of oil spewing from the well.