437 U.S. 1 (1978)
Petitioner Burks was tried in the United States District Court for robbing a federally insured bank by use of a dangerous weapon, in violation of 18 U.S.C. § 2113(d).1 Burks' principal defense was insanity.2 He presented three expert witnesses who, though offering differing diagnoses, testified that he suffered from a mental illness at the time of the robbery that rendered him substantially incapable of conforming his conduct to the law.3 In rebuttal the Government offered testimony of two experts.4 One testified that Burks had a character disorder but was not mentally ill, and another acknowledged a character disorder but gave an ambiguous opinion on Burks' capacity to conform his conduct to the law.5 Several lay witnesses for the Government opined that Burks appeared capable of normal functioning and was sane at the time of the alleged offense.6
Before the case was submitted to the jury, the District Court denied a motion for a judgment of acquittal. The jury found Burks guilty. He then filed a timely motion for a new trial, asserting among other things that the evidence was insufficient to support the verdict. The District Court denied the motion and concluded that Burks' challenge to the sufficiency of the evidence was utterly without merit.7
On appeal Burks narrowed the issues by admitting the affirmative factual elements of the charge and confined his appeal to criminal responsibility. The Court of Appeals agreed that the evidence was insufficient to support the verdict and reversed his conviction. That court noted that once a prima facie defense of insanity has been raised the Government has the burden of proving sanity beyond a reasonable doubt. The Court of Appeals concluded that Burks had met his obligation by presenting specific testimony of three experts with unchallenged credentials and that the prosecution had not effectively rebutted that proof. The prosecution's witnesses failed to express definite opinions on the precise questions the court deemed critical regarding sanity and criminal responsibility.8
The Court of Appeals did not order outright acquittal.9 Instead, it remanded to the District Court for a determination of whether a directed verdict of acquittal should be entered or a new trial ordered.10 It instructed the District Court to choose the appropriate course from a balancing of the equities.11 The United States has not cross-petitioned on the question whether the Court of Appeals was correct on the underlying substantive determination that the Government failed to meet its burden with respect to insanity.12
Whether an accused may be subjected to a second trial when a conviction in a prior trial was reversed by an appellate court solely for lack of sufficient evidence to sustain the jury's verdict?13
The Double Jeopardy Clause of the Fifth Amendment prohibits retrial when a reviewing court determines that the evidence in a prior trial was insufficient to sustain the jury's verdict. Such a reversal is equivalent to an acquittal. The prosecution has already had one fair opportunity to present its case.14
Yes. The Court of Appeals reversed Burks' conviction solely because the evidence was insufficient to support the verdict on the issue of sanity.15 The prosecution had one opportunity to present its case through expert and lay testimony on the question of Burks' sanity after he raised the insanity defense.16 Because the reversal was for insufficiency of the evidence rather than trial error, the Double Jeopardy Clause bars a second trial.17
An accused may not be subjected to a second trial when a conviction in a prior trial was reversed by an appellate court solely for lack of sufficient evidence to sustain the jury's verdict.18