does every US state require a unanimous jury verdict for "not guilty"?

AIUI, in a criminal case tried before a jury anywhere in the US, every member of the jury must vote for a guilty verdict before a guilty verdict can be delivered.

Is the same universally true for a not-guilty verdict? Or are there some US states where a deadlocked jury results in a not-guilty verdict (and therefore a deadlocked jury can’t cause a mistrial)?

Louisiana and Oregon allow convictions by a 10-2 vote. Presumably it works the same way for an acquittal.

Almost, but not quite – in all states but Oregon and Louisiana. I don’t know if anything has changed in the three years since that article was written.

Oregon is quite unusual in allowing non-unanimous verdicts in criminal trials, even for a conviction. IIRC you can be convicted of a felony on a 10-2 vote.

ETA: Ninjaed. I do think Oregon and Louisiana should put an end to that nonsense.

Military panels (which are kinda, sorta but not really the equivalent of civilian juries) in a U.S. court-martial need only a 2/3rds majority to vote guilty for there to be a conviction. But, the flip side is that there are no “hung juries” in a court-martial. If the panel is not able to muster a 2/3rds majority in favor of conviction, a finding of not guilty is required.

So, for example, a general court-martial requires only a minimum of 5 members on the military panel, but let’s say there are six for whatever reason. If there is only one charge to be considered and the panel is split 50/50 with 3 voting in favor of guilty and 3 voting not guilty, the panel is required to come back with a not guilty finding.

SCOTUS recently struck down Florida’s 10-2 rule for jury advisory votes on the death penalty (before that, they’d struck down the previously law that allowed the death penalty based on a 7-5 vote!) A unanimous 6-juror vote is required for any conviction.

But was that just for the death penalty? Because, otherwise, I would expect Louisiana and Oregon’s laws to have brought up in appeals (by someone convicted 10-2).

Yes, just for the DP. So far SCOTUS has not required unanimity for conviction or less-than-capital sentences (unless the jury is composed of fewer than 12 persons).

Interesting. That’s similar to how criminal juries work in Scotland.

But isn’t a hung jury the practical equivalent of “not guilty”, anyway?

No. The jury must unanimously convict or unanimously acquit. A hung jury results in a mistrial - meaning the entire proceeding is thrown out, with everything starting again from scratch. Of course, the state or the defendant may not want to go through a trial all over again, but if they don’t make a deal it means a new trial.

How is that not double jeopardy, then?

IANAL but retrial following a mistrial is not double jeopardy by definition, set by case law.

You can make the argument that a hung jury means that the defendant was not proven guilty beyond a reasonable doubt and should be acquitted, but that’s not what the legal system decided should happen.

Because SCOTUS says so. Perez didn’t really explain the court’s reasoning.

In general, for two reasons, one practical, one theoretical.

The theoretical reasoning is this: double jeopardy rules exist to preclude the state from repetitively charging a specific defendant with charge after charge after charge, each time hoping to manage to get the magic formula right with regard to the charge, the evidence adduced at trial, and the result. So, we don’t want the state trying you for murder the first time emphasizing the circumstantial evidence, and, when that doesn’t work, trying a second time with the somewhat less savoury testimony of an informant, and when that doesn’t work, trying a third time with the introduction into evidence of eye-witnesses who might be less than reliable, etc. With a hung jury, there’s less incentive to tinker with the case because after all, the state didn’t LOSE, it just didn’t WIN (yet).

The practical reasoning is simple: if a hung jury meant you couldn’t re-try the case, then all any defendant would attempt to do is win the vote of one person, and they would be safe. That’s more drastic an approach to due process than we really want.

At common law a hung jury/mistrial could be a bar to further prosecution if to do so would be an abuse of process. Is there something similar in the US?

The trial court generally has some discretion in determining whether to permit retrial.