Sterling's attorneys also have argued that the exams and letters regarding his mental capacity were defective and incomplete, and that there was conspiracy to sell the team without his consent.
The NBA has moved to oust Sterling because of racist remarks he made to a girlfriend.
"The NBA wants to get rid of my client," Sterling attorney Gary Ruttenberg said in court. "They were colluding with Mrs. Sterling and her counsel to do this."
His wife's lawyers claim Donald Sterling has been engaging in tactics to run out the clock on the Clippers sale.
NBA owners are scheduled to vote on the deal on July 15. It's also the day that Ballmer's offer is set to expire — and there is no deal without the judge's approval of the sale.
If the sale isn't completed by Sept. 15, the league said it could seize the team and put it up for auction.
"He will pull out all the stops to prevent the sale from going forward," O'Donnell told Judge Michael Levanas.