Kevin Costner Testifies in Stephen Baldwin's BP Oil Spill Suit

PHOTO: Kevin Costner arrives at the U.S. District Court Eastern District Of Louisiana on June 5, 2012 in New Orleans, Louisiana.PlayMonica McKlinski/Getty Images
WATCH Stephen Baldwin Sues Kevin Costner

During a tense day in court, actor Kevin Costner testified he was heartbroken by the 2010 BP oil spill in the Gulf of Mexico, and he had hoped a device he helped develop could aid the cleanup efforts.

Now, he's being sued by fellow actor Stephen Baldwin, who claims he was duped out of money in a multimillion-dollar deal for the devices between Costner's company and BP.

Costner took the stand for about an hour in a packed New Orleans courtroom, sitting just a few feet away from Baldwin, although the two never made eye contact.

The first day of questioning focused largely on Costner's background in the science and technology business. The "Waterworld" and "Field of Dreams" star told the court he went to New Orleans after the spill on a "fact-finding mission" to see if the device he helped develop could be of any help in the cleanup. At the height of the oil spill cleanup effort, BP bought 32 of the devices for $18 million.

The lawsuit brought by Stephen Baldwin alleges Baldwin and his friend, Spyridon Contogouris, were deliberately excluded from the meeting between Costner, his business partner Patrick Smith, and BP executive Doug Suttles where the incredibly lucrative deal was struck.

Baldwin and Contogouris say they were deceived into letting go of their shares in the new company, Ocean Therapy Solutions, one day before that deal was finalized. They're seeking more than $21 million in damages.

Costner's attorney argues the actor had no role in Baldwin and Contogouris' decision to sell their shares, and that he's only being sued because he's famous.

There were several tense moments during the prosecution's questioning of Costner. When Baldwin's attorney, James Cobb, questioned Costner about whether his celebrity would pressure the oil giant to order his centrifugal machines, Costner countered that he didn't feel the company would buy them just because of him. He admitted he was on the company's radar, but said it was a huge crisis and it was never his intention to use his celebrity to sell the product.

"I'm not just a celebrity," Costner told the court. "I'm not just a person who opens doors."

At another point, Cobb pressed Costner for an answer about whether or not his business partner is authorized to speak on his behalf. Costner struck back.

"I don't do very well when you get very loud," he said to Cobb. "I'm trying to remember as much as I can."

He said he was nervous and his name was at stake in the trial.

Costner has been involved with the development centrifugal device, dubbed the "Costner solution," at the center of the trial for more than 15 years. He previously claimed the machine would "give us a fighting chance to fight back the oil before it got us by the throat."

There was a brief moment of levity during testimony when Costner described the oil-and-water separating device. He noted its large size and equated the footprint to the witness box, which he called a "jail." That elicited a laugh from the courtroom.

Costner is scheduled to take the stand again at 10 a.m. ET Friday.

The Associated Press contributed to this report.