Billionaire Mark Cuban 'cheated' with insider trading: SEC lawyer DALLAS (Reuters) - Mark Cuban, the owner of the Dallas Mavericks basketball team, "cheated" by selling his stake in a small Internet search company upon learning that holding on might cost him money, a government lawyer told jurors at the start of the billionaire's insider trading trial. Cuban has maintained he did nothing wrong more than nine years ago when he sold his 6.3 percent stake in Mamma.com Inc. But a lawyer for the U.S. Securities and Exchange Commission said the 55-year-old knew what he was doing in unloading his stake, and avoiding a $750,000 loss. Cuban rose to prominence ahead of the dot-com crash by selling his company Broadcast.com in 1999 to Yahoo Inc for $5.7 billion. "It's about the right of every investor to trade in a market that's fair," SEC lawyer Jan Folena told a jury of seven women and three men in her opening statement on Tuesday. He cheated and, above all investors, he knew better. Cuban is accused of selling his 600,000 Mamma.com shares in late June 2004, soon after learning from Chief Executive Guy Fauré that the company was planning an equity offering that could dilute his stake. The share price of the Montreal-based company dropped 9.3 percent on the morning after the offering was announced. Thomas Melsheimer, one of Cuban's lawyers, countered in his opening statement that the offering was already public information and Mamma.com had waited to tell Cuban about it, because they knew he would not like it. Cuban has also said in court papers that he had been concerned about Mamma.com's possible links to a known stock swindler, and Melsheimer told jurors that his client had multiple reasons not to remain the company's largest outside shareholder. "He didn't deceive Mamma.com, he didn't deceive anyone," Melsheimer said. He no longer trusted the company. He no longer wanted to be involved with this company. Through the civil case, the SEC is seeking to recoup ill-gotten gains, impose fines and obtain a permanent injunction to bar Cuban from similar alleged misconduct. Cuban and Fauré are both expected to testify. Folena said the SEC would present evidence to prove Cuban sold his stake because of confidential information from Fauré. "Insider trading is a form of cheating," Folena said. It's like knowing the answers to a test before you take it. She also urged jurors, who are hearing the case in Cuban's hometown, not to be swayed by his fame or popularity. "Our laws apply to everyone - the rich, the poor, the famous and the unknown," Folena said. According to SEC court papers, after Cuban learned of the offering plan, he told Fauré, "now I'm screwed. I can't sell. Cuban has maintained that any information he may have received was neither confidential nor material enough to trigger an insider trading violation. On Monday, before jurors were chosen, Cuban told reporters repeatedly, "I won't be bullied." The government shutdown that began on Tuesday is not expected to affect the trial before U.S. District Judge Sidney Fitzwater in Dallas. The trial is expected to last eight to 10 days, possibly stretching into mid-October. Cuban, a star of the ABC television show "Shark Tank," has appeared on ABC's "Dancing with the Stars" and on HBO's "Real Time with Bill Maher." The SEC brought the case against Cuban in November 2008. Reporting by Jana J. Pruet; Writing by David Bailey; Editing by Carol Bishopric