MIAMI  — Jose Padilla’s jury gave the Bush administration the biggest victory it could have Thursday, convicting him and two defendants of supporting terrorism. But some legal experts say it was a loss for the government’s argument that it can’t use civilian courts to prosecute hundreds of detainees suspected of being terrorists.

Padilla, a New York native raised in Chicago, and his foreign-born co-defendants, Adham Amin Hassoun and Kifah Wael Jayyousi, were convicted Thursday by a federal jury of conspiracy to murder, kidnap and maim people overseas, which carries a maximum penalty of life in prison. They were also convicted of two terrorism material support counts, each of which carries a maximum 15-year sentence.

The administration’s preference has been to try accused terrorists at the U.S. naval base at Guantanamo Bay, Cuba, before a military panel. It says it’s difficult to try such cases in civilian court, where suspects have greater rights and secret and sensitive evidence can’t be presented because the proceedings are public.

“This verdict once again demonstrates that federal courts are perfectly capable of handling terrorism cases,” added Neal Sonnett, a prominent Miami defense lawyer who chairs an American Bar Association task force on treatment of enemy combatants.

“It’s going to be difficult for the government to continue the argument that we need military commissions in Guantanamo Bay because we don’t have other options. Well, how did we convict Jose Padilla?” said Scott Silliman, law professor and director of the Duke University Center on Law, Ethics and National Security.