A federal appeals court in Boston has ordered a new trial for a Medford man convicted in 2010 of shining a laser beam at an airborne State Police helicopter in December 2007. In a ruling issued Monday, the US Court of Appeals for the First Circuit threw out Gerard Sasso’s conviction on a charge of willfully interfering with the operation of an aircraft with reckless disregard for human life, on the grounds that jury instruction was flawed. The appeals court also ordered that Sasso, 54, be resentenced for a related conviction of lying to police. He is currently serving a three-year sentence.