How many jurors does it take to deliver a guilty verdict?

In 48 states, the answer is simple: All of them. Juries in felony cases must agree unanimously in order to convict. The rule is the same in federal trials, and for good reason. It reflects the centuries-old understanding that jury unanimity is central to a fair justice system, that it “preserves the rights of mankind,” as John Adams said in 1786.

Yet two states, Oregon and Louisiana, continue to hold out against this fundamental principle. Both permit juries in felony trials to return guilty verdicts even if one or two jurors vote to acquit. Louisiana goes further, allowing split verdicts in murder cases, where convictions can result in sentences of life without parole.

The few remaining defenders of this practice claim that it’s necessary for the “efficient” functioning of the legal system. Here’s a hint: When 48 states and the federal government disagree with you, it’s worth considering the possibility that you might be wrong.

The good news is that Louisiana lawmakers are close to doing that. Last month the State Senate passed a bill to amend the state’s Constitution to require jury unanimity in all felony cases with 12-person juries. (Six-person juries, which try lower-level crimes, are already required to be unanimous.) The House is scheduled to vote on the bill Monday. Lawmakers should approve the measure and send it to the voters for ratification in November. If they fail, they will leave Louisiana trapped under a 19th-century relic that lives on mainly because it makes prosecutors’ jobs easier.