"It's a crime, and Kurt Mix should be held accountable," Justice Department prosecutor Leo Tsao said during the trial's closing arguments.
But a defense lawyer, Michael McGovern, told jurors that the charges against Mix are "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 corrupt bone in his body."
"You did not hear one bad word about Kurt Mix. Not a single one," he said. "Not one bad word about Kurt's character. Not one bad word about Kurt's work."
Mix didn't testify at his two-week-long trial on two counts of obstruction of justice. Each count carries a maximum sentence of 20 years in prison and a $250,000 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, blowout of BP PLC's Macondo well off the coast of Louisiana triggered an explosion that killed 11 workers on the Deepwater Horizon drilling rig and spawned the nation's worst offshore oil spill. Millions of gallons of oil 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, 2010, the day that top kill began, Mix estimated in a text to a supervisor that more than 630,000 gallons of oil per 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 couldn't recover 17 of the messages in the string.
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 federal investigation of the spill, Tsao added.
"Criminal investigations simply cannot work if people are allowed to do what Kurt Mix did," he said.
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 Arabie and a voicemail from Sprague.
McGovern said Mix preserved plenty of evidence, including emails on his BP laptop, that shows there wasn't anything insidious about his deletion of the texts. Investigators chose to ignore that evidence, McGovern added.
"We were the ones who had to show you the truth," he said.
McGovern suggested that Mix could have accidentally deleted the entire string of messages with Sprague when he only intended to erase two photos of himself from the bottom of the string. 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," Tsao said. "He knows how to use his iPhone."
McGovern said it's ludicrous for prosecutors to believe Mix was panicking when he deleted the string of text messages. He showed jurors a photo of Mix smiling during a meeting that was held around the same time Mix deleted the string.
"The government's theory is pure nonsense," McGovern said.
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 in 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 blowout.
Former BP executive David Rainey is charged with concealing information from Congress about the amount of oil spewing from the well.