The Double Jeopardy Clause of the Fifth Amendment to the United States Constitution provides: "[N]or shall any person be subject for the same offence to be twice put in jeopardy of life or limb..." The four essential protections included are prohibitions against, for the same offense: retrial after an acquittal; retrial after a conviction; retrial after certain mistrials; and multiple punishment

Jeopardy attaches in jury trial when the jury is empaneled and sworn in, in a bench trial when the court begins to hear evidence after the first witness is sworn in, or when a court accepts a defendant's plea unconditionally.Serfass v. United States, . Jeopardy does not attach in a retrial of a conviction that was reversed on appeal on procedural grounds (as opposed to evidentiary insufficiency grounds), in a retrial for which "manifest necessity" has been shown following a mistrial, and in the seating of another grand jury if the prior one refuses to return an indictment.

"Same offense" In United States v. Felix, the U.S. Supreme Court ruled: "a[n]...offense and a conspiracy to commit that offense are not the same offense for double jeopardy purposes."United States v. Felix .

Sometimes the same conduct may violate different statutes. If all elements of a lesser offense are relied on to prove a greater offense, the two crimes are the "same offense" for double jeopardy purposes, and the doctrine will bar the second prosecution. This ruling in Felix distinguished between the test in Blockburger and the ruling in Grady v. Corbin regarding the "same conduct" vs "same offense" test, which was later overruled and reverted to Blockburger in United States v. Dixon. In Blockburger v. United States, the Supreme Court held that "where the same act or transaction constitutes a violation of two distinct statutory provisions, the test to be applied to determine whether there are two offenses or only one, is whether each provision requires proof of an additional fact which the other does not".Blockburger v. United States, . The test was applied in Brown v. Ohio, where the defendant had first been convicted of operating an automobile without the owner's consent, and later of stealing the same automobile. The Supreme Court concluded that the same evidence was necessary to prove both offenses, and that in effect there was only one offense. Therefore, it overturned the second conviction.Brown v. Ohio, .

In other cases, the same conduct may constitute multiple offenses under the same statute, for instance where one robs many individuals at the same time. There is no explicit bar to separate prosecutions for different offenses arising under the same "criminal transaction", but it is not permissible for the prosecution to re-litigate facts already determined by a jury. In Ashe v. Swenson, the defendant was accused of robbing seven poker players during a game. John Ashe was first tried for, and acquitted of, robbing only one of the players; the defense did not contest that a robbery actually took place. The state then tried the defendant for robbing the second player; stronger identification evidence led to a conviction. The Supreme Court, however, overturned the conviction. It was held that in the first trial, since the defense had not presented any evidence that there was no robbery, the jury's acquittal had to be based on the conclusion that the defendant's alibi was valid. Since one jury had held that the defendant was not present at the crime scene, the State could not re-litigate the issue.Ashe v. Swenson, .

"Twice put in jeopardy"

Retrial after acquittal Once acquitted, a defendant may not be retried for the same offense: "A verdict of acquittal, although not followed by any judgment, is a bar to a subsequent prosecution for the same offense."Ball v. United States, . This applies in all cases where a verdict of not guilty is entered by the Court against a defendant. Be it an acquittal returned by the finder of fact (jury during a trial by jury, the judge during a bench trialUnited States v. Jenkins, .), a direct acquittal by a judge on motion from the defense,Fong Foo v. United States, or a ruling that the evidence is insufficient for conviction.

Implied acquittals Every charge has specific facts that must be proven beyond reasonable doubt to secure a conviction. And it is not unusual for a prosecutor to charge a person with "lesser included offenses". An oft-mentioned combination is first- and second-degree murder, with second-degree murder being the lesser offense. A person convicted on the lesser charge can never again be tried on the greater charge. If the conviction on the lesser charge is overturned, the greater charge does not then come back into play.

The Supreme Court ruled as such in Green v. United States, establishing the doctrine of "implied acquittal". Everett Green had been tried on charges of arson and first and second degree murder in the U.S. District Court for the District of Columbia. He was convicted on arson and the lesser offense of second degree murder. The verdict was silent on the greater offense. His conviction was overturned due to the appellate court deciding there wasn't enough evidence, remanding for a new trial. At the second trial, he was tried again with arson, first and second degree murder, convicted on the greater offense and sentenced to death.Green v. United States, .

He appealed, claiming the second trial should not have included the greater offense under the Double Jeopardy Clause. The D.C. Circuit Court rejected the claim. The Supreme Court of the United States overruled, stating that Green was acquitted of first degree murder and, under the Fifth Amendment, could not be retried on that charge. At Green's first trial, the jury was authorized to find him guilty of either first degree murder (killing while perpetrating a felony) or, alternatively, of second degree murder (killing with malice aforethought). The jury found him guilty of second degree murder, but, on his appeal, that conviction was reversed and the case remanded for a new trial. At this new trial, Green was tried again, not for second degree murder, but for first degree murder, even though the original jury had refused to find him guilty on that charge and it was in no way involved in his appeal. For the reasons stated hereafter, we conclude that this second trial for first degree murder placed Green in jeopardy twice for the same offense in violation of the Constitution.Green, 355 U.S., at 190.

That the jury did not explicitly return an acquittal on first degree murder in its verdict is immaterial:In brief, we believe this case can be treated no differently, for purposes of former jeopardy, than if the jury had returned a verdict which expressly read: "We find the defendant not guilty of murder in the first degree but guilty of murder in the second degree."Green, 355 U.S., at 191.

This case did, in effect, overrule a preceding per curiam decision, that of Brantley v. Georgia.Brantley v. Georgia, . In that case, the lesser charge was voluntary manslaughter and the greater charge was murder. Brantley was convicted on the lesser charge, but was convicted on the greater charge at retrial after the conviction was overturned. He appealed, arguing the inclusion of the greater charge at retrial violated the Double Jeopardy Clause. The Supreme Court rejected that argument: "It was not a case of twice in jeopardy under any view of the Constitution of the United States."

The Supreme Court explicitly overruled Brantley in another, near-identical case, Price v. Georgia: While the Brantley holding may have had some vitality at the time the Georgia courts rendered their decisions in this case, it is no longer a viable authority and must now be deemed to have been overruled by subsequent decisions of this Court.Price v. Georgia, .

The lesser and greater offenses in Price are identical to Brantley, with both being convicted on the lesser offense, and retried on the same charges as in the original trial after the conviction is overturned. Unlike Brantley, Price was convicted again on the lesser offense of voluntary manslaughter and given a similar sentence. Price appealed that conviction. The State of Georgia contended that since Price was not convicted on the greater offense at retrial, which was the case in Brantley, the second indictment constituted "harmless error". The Supreme Court rejected that idea:The Double Jeopardy Clause, as we have noted, is cast in terms of the risk or hazard of trial and conviction, not of the ultimate legal consequences of the verdict. To be charged and to be subjected to a second trial for first-degree murder is an ordeal not to be viewed lightly. Further, and perhaps of more importance, we cannot determine whether or not the murder charge against petitioner induced the jury to find him guilty of the less serious offense of voluntary manslaughter rather than to continue to debate his innocence.

Noting that the murder charge may have poisoned the jury against Price, the Supreme Court vacated the voluntary manslaughter conviction and remanded the case.

Non-final judgments As double jeopardy applies only to charges that were the subject of an earlier final judgment, there are many situations in which it does not apply, despite the appearance of a retrial. For example, a second trial held after a mistrial does not violate the double jeopardy clause because a mistrial ends a trial prematurely without a judgment of guilty or not, as was decided by the Supreme Court in United States v. Perez.United States v. Perez, . Cases involuntarily dismissed because of insufficient evidence may constitute a final judgment for these purposes, though many state and federal laws allow for substantially limited prosecutorial appeals from these orders. Also, a retrial after a conviction that had been set aside upon a motion for new trial, and that subsequently has been reversed on appeal or vacated in a collateral proceeding (such as habeas corpus) would not violate double jeopardy, for the judgment in the first trial had been invalidated. In all of these cases, however, the previous trials do not entirely vanish. Testimony from them may be used in later retrials, such as to impeach contradictory testimony given at any subsequent proceeding.

Prosecutors may appeal when a trial judge sets aside a jury verdict for conviction with a judgment notwithstanding verdict for the defendant. A successful appeal by the prosecution would simply reinstate the jury verdict and so would not place the defendant at risk of another trial.

Reversal for procedural error If a defendant appeals a conviction and is successful in having it overturned, the defendant may be subject to retrial.

Insufficiency Retrial is not possible if the verdict is overturned on the grounds of evidentiary insufficiency, rather than on the grounds of procedural faults. As noted above, if the trial court made a determination of evidentiary insufficiency, the determination would constitute a final acquittal; in Burks v. United States, the Court held that "it should make no difference that the reviewing court, rather than the trial court, determined the evidence to be insufficient."Burks v. United States .

Fraud If the earlier trial is a fraud, double jeopardy will not prohibit a new trial because the party acquitted has prevented themselves from being placed into jeopardy to begin with. One such case is the trial of Harry Aleman, who was tried and acquitted in 1977 in Cook County, Illinois for the September 1972 death of William Logan. Nearly 20 years later, two persons under Federal Witness Protection came forward to state that Aleman murdered Logan and another individual, and had also bribed the trial judge to return an acquittal.