Determining when jeopardy terminates is no less important than determining when it begins, but it is a little more complicated. Once jeopardy has terminated, the government cannot detain someone for additional court proceedings on the same matter without raising double jeopardy questions. If jeopardy does not terminate at the conclusion of one proceeding, jeopardy is said to be "continuing," and further criminal proceedings are permitted. Jeopardy can terminate in four instances:

1) after acquittal
2) after dismissal
3) after a mistrial
4) on appeal after conviction

A jury's verdict of acquittal terminates jeopardy, and verdicts of acquittal cannot be overturned on appeal even if there is overwhelming proof of a defendant's guilt or even if the trial judge committed reversible error in ruling on an issue at some point during the proceedings. This fundamental maxim of double jeopardy jurisprudence entrusts the jury with the power to nullify criminal prosecutions tainted by egregious misconduct on the part of the police, the prosecutor, or the court, a tremendous bulwark against tyranny in a democratic society.

A jury can also implicitly acquit a defendant. If a jury has been instructed by the judge on the elements of a particular crime and a lesser-included offense, and the jury returns a guilty verdict as to the lesser offense but is silent as to the greater offense, re-prosecution for the greater offense is barred by the Double Jeopardy Clause. For example, a jury that has been instructed as to the crimes of first- and second-degree murder will implicitly acquit the defendant of first-degree murder by returning a guilty verdict only as to murder in the second degree. A not guilty verdict as to the greater offense is inferred from the jury's silence.

Dismissals are granted by the trial court for miscellaneous procedural errors and defects that operate as an absolute barrier to prosecution. For example, the prosecution must establish that a court has jurisdiction over a defendant before prosecution may commence. Failure to establish jurisdiction will normally result in a dismissal upon an objection raised by the defendant. Dismissals may be entered before a jury has been impaneled, during trial, or after conviction. But jeopardy must attach before a dismissal implicates double jeopardy protection.

Once jeopardy attaches, a dismissal granted by the court for insufficient evidence terminates jeopardy and bars further prosecution with one exception. The prosecution may appeal a dismissal entered after the jury has returned a guilty verdict. If the appellate court reverses the dismissal, the guilty verdict can be reinstated without necessitating a second trial. A dismissal granted for lack of evidence after a case has been submitted to a jury, but before a verdict has been reached, may not be appealed by the state.

Reprosecution is permitted and jeopardy continues against the defendant when a case is dismissed by the court at the defendant's request for reasons other than sufficiency of the evidence. For example, courts may dismiss a case when the defendant's right to a speedy trial has been denied by prosecutorial pretrial delay. The Supreme Court has held that no double jeopardy interest is triggered when defendants obtain a dismissal for reasons unrelated to their guilt or innocence (see United States v. Scott, 437 U.S. 82, 98 S.Ct. 2187, 57 L.Ed.2d 65 [1978]).

Mistrials are granted when it has become impracticable or impossible to finish a case. Courts typically declare mistrials when jurors fail to unanimously reach a verdict. Like dismissals, mistrials declared at the defendant's behest will not terminate jeopardy or bar re-prosecution. Nor will a mistrial preclude re-prosecution when it is declared with the defendant's consent. Courts disagree whether a defendant's mere silence is tantamount to consent.

A different situation is presented when a mistrial is declared over the defendant's objection. Reprosecution will be allowed only if the mistrial resulted from "manifest necessity," a standard more rigorous than "reasonably necessary" and less exacting than "absolutely necessary." A mistrial that could have been reasonably avoided will terminate jeopardy, but jeopardy will continue if the mistrial was unavoidable.

The manifest necessity standard has been satisfied where mistrials have resulted from defective indictments, disqualified or deadlocked jurors, and procedural irregularities willfully occasioned by the defendant. Manifest necessity is not present when mistrials result from prosecutorial or judicial manipulation. In each of these cases, courts balance the defendant's interests in finality against society's interest in a fair and just legal system.

Every defendant has the right to at least one appeal after conviction. If the conviction is reversed on appeal for insufficient evidence, it is treated as an acquittal, and further prosecution is not permitted. However, a defendant may be re-prosecuted when the reversal is not based on lack of evidence. The grounds for such reversals include defective search warrants, unlawful seizure of evidence, and other so-called "technicalities." Retrials in these instances are justified by society's interest in punishing the guilty. Defendants' countervailing interests are subordinated when a conviction rendered by 12 jurors is overturned for reasons unrelated to guilt or innocence.