The Supreme Court's decision in Blueford v. Arkansas is yet another tightening of the screw on when double jeopardy attaches. Now, to be fair, the Court's inconsistency and obvious discomfort with the Double Jeopardy Clause goes back decades, if not a century. So, in that sense, this isn't going to be another in my series of posts depicting the Roberts Court as activist judges; this is, instead, a continuation of the 50 year deflation of a protection whose contours have been at times narrower than today's rulings leave it, but which has been receding from a high water mark since I first became interested in the law.
If you don't feel like reading the full decision, linked above, the Times's summary is pretty good. To condense it still further, the Court found that a jury's deadlocking on lesser charges deprived the acquittal of sufficient finality to constitute double jeopardy in retrying the defendant, where the trial court instructed the jury to only consider the lesser charges if the jurors voted to acquit on the higher charges. The dissenters, per Justice Sotomayor, wrote that the trial court erred in not taking a partial verdict on those higher charges.
Again, it would be unfair to call this a deviation from well established precedent, or a flagrant instance of activism. It's just a continued reduction in the scope of protection against double jeopardy.
(Edited for grammar. Oops.)