DALLAS Dallas Mavericks owner Mark Cuban spent Thursday morning on the stand answering questions from federal prosecutors in the insider trading case against him.

The Securities and Exchange Commission is using Cuban's email and blog posts in an attempt to show that Cuban dumped stock in an internet search company based on confidential information given to him by the company's CEO, avoiding $750,000 in losses.

Cuban's defense says the the information Cuban had, when he traded, was already known in financial markets. His legal team also says Cuban had deep concerns about possible fraudulent business practices at the company, the Canadian-based

The website's CEO testified on Wednesday that he told Cuban he planned to sell more shares to the public during a phone call. This upset the billionaire Mavericks owner as it would dilute his shares, the CEO testified.

He argued that Cuban became upset when he realized he couldn't sell his shares until the company announced the stock offering. Cuban has denied any wrongdoing.

On Thursday morning, the SEC began laying the groundwork to question Cuban's credibility.

Cuban's demeanor toward prosecutor Jan Folena has been calm and polite yet still defiant as he picked apart yes and no questions with detailed responses. The strategy seems to be an effort to prove the government's case is not as cut and dry as it claims.

The case is a civil lawsuit. The SEC wants Cuban to pay a fine, but he isn't charged with a crime.

The Associated Press contributed to this report

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