Updated

WASHINGTON (AP) — The Supreme Court has ruled that a minimum 30-year prison term for crimes involving a machine gun may not be imposed unless a jury specifically convicts a defendant of using a machine gun.

The court on Monday unanimously upheld a federal appeals court ruling that had been challenged by the government. The decision came in the case of Martin O'Brien and Arthur Burgess, who were charged in connection with a failed robbery of an armored car carrying $2 million in the Boston area in 2005.

O'Brien and Burgess were indicted on several counts, including carrying a machine gun in the commission of a crime. Federal prosecutors dismissed the machine gun count because they believed they could not prove it to a jury beyond a reasonable doubt.

But they asked the judge to consider the machine gun charge, and the related 30-year prison term, in sentencing the defendants. The judge refused, the federal appeals court in Boston agreed with the judge and the government appealed the case to the high court.

The case is U.S. v. O'Brien, 08-1569.