Samuel and Charles Wyly of Dallas used a web of offshore trusts to illegally hide their stock holdings and evade trading limits, a federal court jury found, leaving Sam Wyly and his late brother’s estate potentially liable for as much as $550 million.The panel of eight women and four men delivered the verdict in favor of the Securities and Exchange Commissionon in a New York federal courtroom on Monday. The regulator claimed the brothers, founders of Irving-based Michaels Stores, hid ownership of shares of companies on whose boards they sat and broke disclosure regulations by failing to reveal the full extent of their offshore holdings. “We will continue to fight for justice through the next phases of the legal process,” said Stephen Susman, an attorney representing Wyly, in a statement after the verdict. “We maintain that Sam and Charles Wyly acted in good faith.”The verdict, delivered after two and a half days of deliberations, is the latest trial win by the SEC in the Manhattan courthouse. A jury in August found former Goldman Sachs Group vice president Fabrice Tourre liable for his role in structuring a failed $1 billion investment. The regulator brings few cases to trial and it took more than a decade to do so with the Wylys — so long that Charles died leaving his estate as a defendant. Sam Wyly, who testified in his own defense during the trial, did himself little good, according to one juror, retired letter carrier Kevin Rothman. Wyly “maybe wasn’t all that sharp” on the stand, he said. “They felt they would put him on the stand because this was his case,” Rothman said one of Wyly’s lawyers told jurors in a closed-door session after the verdict. “This was his ballgame.” Rothman said one female juror was “a little bit of a holdout” against a verdict for the SEC. But that person was persuaded after about a day and a half, he said. Jurors found in favor of the SEC on all nine of its claims against the Wylys.The SEC seeks to impose penalties and force Sam Wyly, 79, and his brother’s estate to turn over $550 million of allegedly illegal gains. U.S. District Judge Shira Scheindlin, who oversaw the trial, will determine whether the Wylys committed insider trading after hearing arguments from both sides. Scheindlin set Aug. 4 for the start of a three-day trial that will also determine how much the Wylys will have to pay. The SEC, among its claims, alleged the Wylys made $31.7 million by using inside information they gained from sitting on the board of Sterling Software Inc. to accumulate shares in 1999, ahead of the company’s $4 billion sale to Computer Associates International.The Wylys claimed they used the offshore trusts for tax purposes, estate planning and asset protection. They said they never concealed the offshore trusts and relied on the advice of “an army of lawyers” they trusted to ensure they complied with the law. During the trial, SEC lawyers presented witnesses, including Michael French, the Wylys’ former lawyer who settled with the regulator before the trial. Several testified that the Wylys exercised control over the offshore trusts through trustees who always complied with their orders. “We will continue to hold accountable, and bring to trial when necessary, those who commit fraud no matter how complex their scheme or how hard they try to hide it,” Andrew Ceresney, the SEC’s enforcement director, said in a statement following the verdict. In his testimony, Sam Wyly insisted that he had not violated federal securities laws and said trustees on the Isle of Man had acted independently, approving transactions without his direction. Charles Wyly died in August 2011 when his 1983 Porsche Targa was hit by another vehicle near Aspen.