If a defendant in Oregon is going to trial on any felony other than murder, the jury will likely be instructed that of the 12 jurors, only 10 need to vote guilty to convict. Oregon is the only state in the country that allows the jury to be so instructed. Next term, the Supreme Court of the United States will decide whether that instruction violates the federal Constitution. For details, go here.
In light of the fact that a US Supreme Court ruling is (relatively speaking) imminent, even the most modestly competent defense attorneys in Oregon will object to that instruction and ask that only a unanimous verdict can be the basis for guilt. Prosecutors will oppose. Should they?
First, prosecutors will argue that they are required by the Oregon Constitution to oppose, since they interpret the Oregon Constitution to mandate non-unanimous verdicts, as opposed to merely allowing non-unanimous verdicts. I think that reading is absurd, but if the local DA believes it, then the discussion is over. In their minds, they have no choice but to oppose any unanimity requirement.
But assume a local DA realizes that (1) he can lawfully agree to instruct the jury on the need for unanimity and (2) there is at least a 50/50 chance that non-unanimous verdicts will be declared unconstitutional. Should the DA reduce the risk of an appellate reversal of any convictions by conceding the issue, at least temporarily, now?
It's a fun hypothetical but I would be shocked if any DA made such a concession, no matter how sound it would be to do so. My experience has been such that prosecutors would willingly increase the odds of a reversal, sometimes significantly, than make it even a little harder to get a conviction. There is a reason so many arguments that I have encouraged over the years have resulted in reversals and will do so for decades to come. There are institutional and professional incentives to get the conviction now, at all costs, regardless of the expense of a possible reversal, and the pain it might bring to victims and their families.
(I would note that it's not either/or. If the prosecutor is wrestling with whether to offer a piece of evidence, knowing it's helpful but not essential but also likely to increase the chances of a reversal, the simple solution is to make the defendant a better plea offer.)
In this situation, the usual conflict between getting a conviction and risking a reversal is much more stark than normal. A favorable ruling from SCOTUS could result in dozens of reversals, at great expense and inconvenience.
Prosecutors who support non-unanimous verdicts often claim that, if unanimity were required, the results wouldn't change much, because eventually the hold-outs would eventually agree with the majority. Or in the rare case of a mistrial due to a hung jury, there would be unanimity the next time around. If prosecutors really believe that, then agreeing to unanimity now would seem to minimize the risk of a massive number of reversals in exchange for only mild inconvenience.
But I think prosecutors mostly realize, their public claims notwithstanding, that unanimity would be a hardship for them. Not that there would be that many more hung juries, but that there would be a lot more compromise verdicts. That is, if jurors are 10-2 to convict of Robbery I, rather than telling the court they're hung, they might agree to convict unanimously of Robbery II. It may not be completely satisfying, but jurors want to reach a verdict, they want to get the job done, and if there is a way to do so, they will find it. A compromise verdict is often the most reasonable way forward.
If and when these cases come back in 2-3 years, if a civil trial can't get out because all these criminal cases are being re-tried, if victims have to relive the trauma of trial, remember this: when a case gets reversed, it is the prosecutor's fault. They won't tell you that. They'll blame the appellate judges. And technically, it's the trial judge who is reversed, but only because he or she did what the prosecutor asked them to.