Costner, who has been sued in a multimillion-dollar business dispute involving the devices, testified Thursday for about an hour at the trial of the lawsuit in U.S. District Court in New Orleans.
Fellow actor Stephen Baldwin and Baldwin's friend, Spyridon Contogouris claimed Costner and a business partner duped them of their share of an $18 million deal for BP to buy the oil-separating centrifuges after the 2010 oil spill.
Costner is expected to resume testifying Friday. His lawyer has denied the lawsuit's claims.
