By MICHAEL A. LINDENBERGER

Even Americans who know very little about the U.S. Constitution know this much: once a jury decides you are innocent of a crime, the government can’t keep hauling you back into court to try your case over again. It’s called the prohibition on double jeopardy, and it’s in the Bill of Rights because the Founding Fathers thought it was an essential bulwark against tyranny. But like most truisms in American law — that the police have to read you your rights before they question you, that it takes a unanimous verdict to be convicted, or that the police need a warrant to search your house — there are exceptions large enough to drive a prison bus through.

The Supreme Court this week decided to hear a case out of Arkansas that will test just how big the exceptions to the double-jeopardy protection contained in the Fifth Amendment are, and experts say the decision could resolve long-standing differences between the states about when it’s O.K. for the government to retry defendants when it can’t get a conviction the first time. Because of the nature in which the decisions were made in Arkansas, the U.S. Supreme Court could use the case to decide what constitutes an official verdict. (Read about your Bill of Rights and pleading the Fifth Amendment.)

Arkansas prosecutors want to try Alex Blueford on capital-murder charges because they believe he hit his girlfriend’s 19-month-old toddler, Thomas McFadden Jr., so hard that the boy’s eyes bled and his brain swelled so much that he died.

Trouble is, the state has already tried him once and without success. There is no question it was an ugly set of circumstances. During the 2009 trial, Blueford told jurors he had lied repeatedly to the doctors as they rushed to save the boy’s life because he was afraid no one would believe him when he explained that his elbow connected to the side of Thomas’ head only after the boy (nicknamed Fat Man, according to news reports covering the trial) had startled him from behind. He insisted it was an accident. The jurors apparently believed him. After about 4½ hours of deliberations, the jury forewoman sent a message to the judge saying they were having trouble deciding. Back in open court, according to a partial court transcript, the jury forewoman explained that they had voted unanimously — 12 to 0 — for acquittal on the capital-murder charge, and then voted 12 to 0 for acquittal on a charge of first-degree murder. But they were split over a third charge, manslaughter, for which the vote was 9 to 3 to convict. They hadn’t yet begun discussing a fourth charge, a misdemeanor charge of negligent homicide, which would have resulted in Blueford’s immediate release.
Blueford’s attorneys asked the judge to enter the announcement as a verdict on the two most serious charges, but the judge declined. He told the jury to try again and when they reported they were still deadlocked on the manslaughter charge, he immediately declared a mistrial.

Prosecutors moved quickly to bring charges against Blueford a second time and readied for a second trial. His attorneys asked the Arkansas Supreme Court to throw out the two murder charges, arguing that another trial would be exactly the kind of double jeopardy the Bill of Rights is designed to protect against. The court disagreed, noting that the forewoman’s statements in open court about the unanimous votes to acquit didn’t amount to a real verdict because the decisions were never written down on a verdict form and entered into the record. “It is axiomatic that a judgment is not valid until entered of record,” the Arkansas Supreme Court ruled in January. “We further stated in [a previous case] that a judgment rendered in open court is not controlling until entered or filed of record. The mere reading of the jury’s verdict in open court does not constitute an acquittal.” (Watch a video over the Supreme Court.)

That a defendant would have to endure a second trial after a seeming victory in the first round is nothing new. Prosecutors routinely retry defendants after a hung jury. And they often win on their second crack at the case: just ask former Illinois governor Rod Blagojevich in Chicago. The first time out, federal prosecutors were only able to win a conviction on a single, relatively minor charge — out of 24 — and Blagojevich all but declared victory. A year later, however, they were all back in court and jurors saw things much differently. The U.S. got him on 17 of the 20 charges, including many that he had seemed to beat on the first round.

But Blueford’s case is different, say his attorneys and dozens of law professors and others who have filed friend-of-the-court briefs in his support. For one thing, the jury didn’t fail to agree that he was guilty — as with Blagojevich’s first case — they actually voted on both serious charges, and in both cases were unanimous that he was innocent. Lawyer Charles Curtis, a partner at Arnold & Porter LLP working pro bono on the case, co-wrote an amicus brief on behalf of more than a dozen criminal-law professors supporting Blueford’s request for a Supreme Court hearing. He told TIME that allowing the Arkansas Supreme Court’s ruling to stand in this case would be a triumph of form over substance. Just because a jury’s unanimous decision isn’t read into the record as a formal verdict, and filed in written form, it doesn’t mean the 12 jurors hadn’t made a decision. They had, he argued.
“This is an especially compelling case,” he told TIME this Wednesday. “In Arkansas, they have what is known as a hard transition rule, which means that jurors are instructed that they cannot consider a lesser included charge until after they have already come to a unanimous decision against convicting on the more serious charge. They have to go in order, which is usually a gift to the prosecutors. They have to convict on the most serious charge they can agree on, and can’t skip to a lesser offense.” (Read a review of Five Chiefs, Justice John Paul Stevens’ Supreme Court memoir.)

In a second amicus brief, on behalf of the Constitutional Accountability Center, a liberal think tank and law firm, lawyers argued that the Fifth Amendment was designed in part to protect against the government’s influence over judicial proceedings, and that “fundamental principles do not lose their force here simply because the jury that heard Blueford’s case was not able to resolve all of the charges against him … The Fifth Amendment’s prohibition on double jeopardy protects the jury’s judgment that the defendant is not guilty of the charges and is entitled to an acquittal, not the ministerial act of reducing their vote to a judgment.”

Arkansas sees it differently, of course. The attorney general’s office argues that the trial transcript reveals nothing more than “that a discussion transpired between the trial judge and the jury foreperson without any attendant formalities and before the jury had concluded its deliberations.” Its lawyers argue that the state supreme court got it right when it ruled against Blueford in an opinion that “speaks to the well-established requirement that any final verdict must be presented and received in such manner that each juror appreciates the finality and gravity of the verdict and unanimously affirms it.”

The nine Justices in Washington will have the final say about who got it right when they issue their ruling, which isn’t expected until sometime next year.