I'm pretty sure I briefed this issue (i.e., retrial after jury mistrial, not a bench mistrial) in the 4th Circuit a long, long time ago, but the operative issue is the reason for the mistrial.  There must be "manifest necessity" for declaring a mistrial before the state will be allowed to retry consistent with DJ principles.  That case is US v. Perez from 1824 (no, I did not remember the year off the top of my head).  The burden of proving the manifest necessity of the prior cessation of proceedings is on the government, so the failure of the judge to make findings supporting his (non)decision might not hurt the defendant.  In looking for the Perez info, I came across the following discussion from Justice Douglas in an unavailable witness mistrial case, Downum v. US.  I know this is all academic, but that's one of the dumbest things I've ever heard.   . . .

  From United States v. Perez, 9 Wheat. 579, 6 L.Ed. 165, decided in 1824, to Gori v. United States, 367 U.S. 364, 81 S.Ct. 1523, 6 L.Ed.2d 901, decided in 1961, it has been agreed that there are occasions when a second trial may be had although the jury impaneled for the first trial was discharged without reaching a verdict and without the defendant's consent. The classic example is a mistrial because the jury is unable to agree. United States v. Perez, supra; Logan v. United States, 144 U.S. 263, 298, 12 S.Ct. 617, 628, 36 L.Ed. 429; Dreyer v. Illinois, 187 U.S. 71, 85—86, 23 S.Ct. 28, 32—33, 47 L.Ed. 79; Keerl v. Montana, 213 U.S. 135, 29 S.Ct. 469, 53 L.Ed. 734. In Wade v. Hunter, 336 U.S. 684, 69 S.Ct. 834, 93 L.Ed. 974, the tactical problems of an army in the field were held to justify the withdrawal of a court-martial proceeding and the commencement of another one on a later day. Discovery by the judge during a trial that a member or members of the jury were biased pro or con one side has been held to warrant discharge of the jury and direction of a new trial. Wade v. Hunter, supra, 336 U.S. 689, 69 S.Ct. 837, 93 L.Ed. 974; Simmons v. United States, 142 U.S. 148, 12 S.Ct. 171, 35 L.Ed. 968; Thompson v. United States, 155 U.S. 271, 15 S.Ct. 73, 39 L.Ed. 146. At times the valued right of a defendant to have his trial completed by the particular tribunal summoned to sit in judgment on him may be subordinated to the public interest—when there is an imperious necessity to do so. Wade v. Hunter, supra, 336 U.S. 690, 69 S.Ct. 837—838, 93 L.Ed. 974. Differences have arisen as to the application ofthe principle. See Brock v. North Carolina, 344 U.S. 424, 73 S.Ct. 349, 97 L.Ed. 456; Green v. United States, 355 U.S. 184, 188, 78 S.Ct. 221, 223—224, 2 L.Ed.2d 199. Harassment of an accused by successive prosecutions or declaration of a mistrial so as to afford the prosecution a more favorable opportunity to convict are examples when jeopardy attaches. Gori v. United States, supra, 367 U.S. 369, 81 S.Ct. 1526—1527, 6 L.Ed.2d 901. But those extreme cases do not mark the limits of the guarantee. The discretion to discharge the jury before it has reached a verdict is to be exercised 'only in very extraordinary and striking circumstances,' to use the words of Mr. Justice Story in United States v. Coolidge, 25 Fed.Cas. 622, 623. For the prohibition of the Double Jeopardy Clause is 'not against being twice punished, but against being twice put in jeopardy.' United States v. Ball, 163 U.S. 662, 669, 16 S.Ct. 1192, 1194, 41 L.Ed. 300. The jury first selected to try petitioner and sworn was discharged because a prosecution witness had not been served with a summons and because no other arrangements had been made to assure his presence. That witness was essential only for two of the six counts concerning petitioner. Yet the prosecution opposed petitioner's motion to dismiss those two counts and to proceed with a trial on the other four counts—a motion the court denied. Here, as in Wade v. Hunter, supra, 336 U.S. at 691, 69 S.Ct. at 838, 93 L.Ed. 974, we refuse to say that the absence of witnesses 'can never justify discontinuance of a trial.' Each case must turn on its facts. On this record, however, we think what was said in Cornero v. United States, supra, states the governing principle. There a trial was first continued because prosecution witnesses were not present, and when they had not been found at the time the case was again called, the jury was discharged. A plea of double jeopardy was sustained when a second jury was selected, the court saying:  

'The fact is that, when the district attorney impaneled the jury without first ascertaining whether or not his witnesses were present, he took a chance. While their absence might have justified a continuance of the case in view of the fact that they were under bond to appear at that time and place, the question presented here is entirely different from that involved in the exercise of the sound discretion of the trial court in granting a continuance in furtherance of justice. The situation presented is simply one where the district attorney entered upon the trial of the case without sufficient evidence to convict. This does not take the case out of the rule with reference to former jeopardy. There is no difference in principle between a discovery by the district attorney immediately after the jury was impaneled that his evidence was insufficient and a discovery after he had called some or all of his witnesses.' 48 F.2d at 71, 74 A.L.R. 797.6

That view, which has some support in the authorities,1 is in our view the correct one. We resolve any doubt 'in favor of the liberty of the citizen, rather than exercise what would be an unlimited, uncertain, and arbitrary judicial discretion.'2 This means that the judgment below must be and is reversed.

. . . .

  Hardy Lewis Blanchard, Miller, Lewis & Styers, P.A. 1117 Hillsborough Street Raleigh, North Carolina 27603 919.747.8107 (Direct) 919.755.3993 (Firm) 919.755.3994 (fax)
Also look at U.S. v. Dinitz, 424 U.S. 600 (1976), Wade v. Hunter, 336 U.S. 684 (1949), Oregon v. Kennedy, 456 U.S. 667 (1982), Benton v. Maryland, 395 U.S. 784 (1969).   And state cases, State v. Brunson, 96 N.C. 244 (1990) and State v. Case, 268 N.C. 330 (1966)