WASHINGTON — The U.S. Supreme Court on Wednesday struggled with whether to require new trials for potentially thousands of prisoners who were convicted by non-unanimous juries before the court barred the practice earlier this year.The high court ruled 6-3 in April that juries in state criminal trials must be unanimous to convict a defendant. Previously, Louisiana and Oregon as well as the U.S. territory of Puerto Rico had allowed divided votes to result in convictions. In striking down the practice, the court said …