The Supreme Court on Wednesday struggled with whether to require new trials for potentially thousands of prisoners in Louisiana and Oregon who were convicted by non-unanimous juries before the court barred the practice last year.

The high court last year ruled 6-3 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. Now, juries everywhere must vote unanimously to convict.

But the Supreme Court's decision last year affected only future cases and cases in which the defendants were still appealing their convictions when the high court ruled. The question for the court now is whether the decision should be made retroactive. That would benefit prisoners convicted by non-unanimous juries whose cases were final before last year's ruling.

Several justices noted the very high bar past cases have set to making a new rule retroactive while also suggesting this case might clear it. “Why isn't unanimity basic?” Justice Stephen Breyer asked during arguments the court heard by phone because of the coronavirus pandemic. “How could it be that a rule like that does not have retroactive effect?” Justice Elena Kagan asked.