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Burden of Proof


The principal purpose of most trials is to resolve a dispute about facts. Both parties present evidence to a fact finder, either judge or jury, who evaluates the evidence and resolves the controversy. A number of rules of law guide the fact finder in evaluating the evidence; most important of these are the rules that tell the fact finder who should have the benefit of the doubt.

These rules are typically expressed as statements about which party must carry the burden of proof, and how heavy the burden is. For example, in most civil cases, the plaintiff has the burden of proof, and the burden is to prove the case "by a preponderance of evidence." In criminal cases, it has long been the general rule that the prosecution has the burden of proof, and the burden is to prove guilt "beyond a reasonable doubt."

The reasonable doubt rule

In 1970 the U.S. Supreme Court declared that the Constitution required the reasonable doubt rule in criminal cases. In the case of In re Winship, 397 U.S. 358 (1970), the Court held that the "Due Process Clause protects the accused against conviction except upon proof beyond a reasonable doubt of every fact necessary to constitute the crime with which he is charged" (p. 364).

Winship restated the general understanding of the rule governing proof in a criminal case, and therefore it was not especially controversial. At the same time, however, by articulating a constitutional basis for the rule, Winship laid the foundation for litigation over the proper scope of this newly articulated constitutional rule.

One question is whether the rule applies in contexts that are not criminal prosecutions, but are similar in some respects to criminal cases. Winship itself extended the rule from ordinary criminal cases to certain types of juvenile delinquency proceedings. In general, the Court has declined to hold that the rule is required in noncriminal proceedings, although it has held that sometimes the Constitution requires the government to prove its case by the intermediate standard of "clear and convincing evidence." For example, the state must prevail by clear and convincing evidence in proceedings for compulsory psychiatric hospitalization (Addington v. Texas, 441 U.S. 418 (1979)) and in proceedings to terminate parental rights (Santosky v. Kramer, 455 U.S. 745 (1982)).

A second controversial question is whether the rule applies to every issue in a criminal case, or whether particular issues may be excluded from the rule. Although most states have long adhered to the general rule that the prosecution must prove guilt beyond a reasonable doubt, each state also has developed its own idiosyncratic list of exceptions, requiring defendants to prove such issues as self-defense, duress, insanity, entrapment, renunciation, and mistake.

State criminal codes frequently use the term defense or affirmative defense to describe an issue where the burden of proof is assigned to the defendant. Other codes simply state that the burden of proof for all issues is on the state except where the statute expressly states otherwise.

Both the reasonable doubt rule and some of its exceptions have relatively ancient roots. The reasonable doubt rule has been recognized in Anglo-American law at least since 1798, and probably for several centuries before that (May; Morano; Green). Exceptions to the rule were also apparently recognized in the eighteenth and nineteenth centuries (Fletcher). But not until the rule acquired constitutional standing in 1970 did courts begin to seek criteria to govern its application, and the search has not been an easy one.

In a pair of very similar cases decided soon after Winship, the Court reached virtually opposite conclusions. Both cases involved statutes that shifted to the defendant the burden of proving that the crime was not murder but only the less serious crime of manslaughter. In Mullaney v. Wilbur, 421 U.S. 684 (1975), the Court had invalidated a state statute requiring the defendant to prove provocation, but two years later, in Patterson v. New York, 432 U.S. 197 (1977), the Court, without overruling Mullaney, upheld a statute requiring the defendant to prove "extreme emotional disturbance." The Court found a critical distinction in the way the two statutes were written: the Mullaney statute defined murder as including the absence of provocation, while the Patterson statute defined murder without reference to extreme emotional disturbance, which it defined separately as a defense. The Court seemingly gave states considerable leeway to make drafting choices that would determine which facts constitute elements of a crime, and must therefore be proved beyond a reasonable doubt.

In the following decade, the Court said little more about when the reasonable doubt rule applied. In the few cases it did decide, the Court favored the approach it took in Patterson, giving considerable leeway to the states in this regard. In Martin v. Ohio, 480 U.S. 228 (1987), for instance, the Court held that even though the defendant would have been entirely innocent of murder if her claim of self-defense were true, the state could require her to prove she had acted in self-defense because the state had not defined murder as including the absence of self-defense.

The rule's scope became controversial again, however, as legislatures increasingly began to draft statutes that specified particular sentencing factors, and courts began to consider whether such factors should be governed by the reasonable doubt rule. A sentencing factor is a fact that determines not what crime a defendant committed, but what sentence the defendant can receive. For example, drug laws frequently dictate that the sentence for possessing or selling drugs shall be increased by a certain number of years as the quantity possessed increases. A sentencing factor also may take the form of a "mandatory minimum," which means that if the factor is present, the defendant must serve at least a specified number of years, greater than the minimum sentence otherwise prescribed for the crime. A sentencing factor, therefore, may be of critical importance in determining how many years a defendant will serve in prison.

While the idea that certain facts, like possessing large quantities of drugs, should lead to harsher sentences is not particularly controversial, the procedure for determining those facts has become quite controversial. Statutes commonly provide that sentencing factors are determined at a sentencing hearing by a judge using a "preponderance of the evidence" standard. In McMillan v. Pennsylvania, 477 U.S. 79 (1986), the Court upheld a statute authorizing a judge to impose a mandatory minimum five-year sentence if the judge found by a preponderance of the evidence that the defendant had possessed a firearm during the commission of a criminal offense. By the late 1990s, however, members of the Supreme Court began voicing concern that sentencing factors were in effect circumventing the protections of the reasonable doubt rule. In 2000, the issue reached a constitutional boiling point in Apprendi v. New Jersey, 120 S. Ct. 2348 (2000).

In Apprendi, the defendant had fired shots into the home of an African-American family that had recently moved into an all-white neighborhood. A state statute provided that using a firearm to shoot into a home would ordinarily carry a sentencing range of five to ten years, but that if the crime was motivated by racial bias, the sentencing range rose to ten to twenty years. Despite Apprendi's denial at the sentencing hearing that he had acted out of racial bias, a judge found by a preponderance of the evidence that Apprendi had been so motivated and sentenced him to twelve yearstwo more years than the maximum sentence of ten years he could have received if the judge had not found the sentencing factor to be present.

The Supreme Court held that because Apprendi received a sentence that was greater than the maximum sentence he otherwise could have received without the sentencing enhancement, due process required that the sentencing factor of racial bias be proven to a jury beyond a reasonable doubt. But the Apprendi case does not necessarily apply the reasonable doubt rule to every sentencing factor that increases a defendant's punishment; the Court declined to disturb an earlier decision holding that when a defendant's prior convictions are used to increase his maximum sentence, the prior crimes need not be proved to a jury beyond a reasonable doubt (Almendarez-Torres v. United States, 523 U.S. 224 (1998)), and it also implied that when aggravating factors are required before the death penalty can be imposed, the aggravating factors need not be proved to a jury beyond a reasonable doubt. The scope of the rule in this area remains unclear, including whether the reasonable doubt rule applies to sentencing factors that increase the defendant's punishment within the statutory range, but do not increase the maximum punishment authorized by statute. Because sentencing factors are so widely used to calculate sentences, the answer to this question is crucial to the future of sentencing in the United States.

The courts are likely to struggle in the coming years with this question and other situations involving the reasonable doubt rule. In resolving such questions, it is useful to consider the rule's purposes.

Reasons for the rule

In justifying its holding, the Winship Court invoked the two distinct functions that generally are attributed to the reasonable doubt rule. First, the rule is meant to reduce the likelihood of erroneously convicting an innocent defendant. It puts a thumb on the defendant's side of the scales of justice to implement "a fundamental value determination of our society that it is far worse to convict an innocent man than to let a guilty man go free" (Winship, p. 372, Justice Harlan concurring).

Second, the rule symbolizes for society the great significance of a criminal conviction by singling out criminal convictions as peculiarly serious among the adjudications made by courts. The rule reaffirms the special opprobrium that attaches to criminal convictions, and the special importance of protecting individuals against the state's power to convict.

There are, of course, empirical questions about whether the rule in practice has its intended effect. The available studies are inconclusive, but they suggest that the instruction on the burden of proof can affect the outcome of a case (L.S.E. Jury Project; Simon, 1969, 1970; Simon and Mahan).

Issues that should be governed by the rule

Commentators have suggested different approaches for deciding which issues should be governed by the reasonable doubt rule. At one extreme, the rule might apply to every issue, without exception, governing the proof of every fact that the criminal law makes relevant to a criminal conviction. At the other extreme, the rule might apply only to those issues for which the legislature has made no explicit exception. The Supreme Court has plainly rejected both extreme positions in Mullaney and Patterson. Under these cases some exceptions are permitted, but there are constitutional limits on the legislature's power to make exceptions. Although the Court has not specified the criteria for permissible exceptions, commentators have suggested several.

First, and least controversial, is the view that the Constitution permits an exception for issues in a criminal case that do not directly relate to guilt or innocence. In the course of a criminal prosecution, it may be necessary to decide whether the case is properly before the court, whether particular items may be admitted into evidence, or whether the defendant is mentally competent to stand trial. These decisions may well determine whether it is possible as a practical matter to convict the defendant, but they do not determine whether the defendant is in fact guilty. For that reason, the Constitution does not impose the reasonable doubt rule on such determinations, although the rule may nonetheless be required as a matter of state law.

A second, more controversial proposal is an exception for issues that present special problems of proof. It is suggested that the defendant should bear the burden of proof on an issue if the defendant has better access than the prosecution to the evidence. The rationale is that a defendant with control over the relevant evidence has a great incentive to withhold the evidence, mislead the jury, and prevail because of the prosecution's inability to meet its burden of proof. This strategy could be prevented by a rule shifting the burden of proof to the defendant. On this theory, the burden of proof might be assigned to the defendant on the issue of insanity or of intent. The problem with shifting the burden to the defendant for this reason is that it accomplishes too much. It not only elicits evidence from the defendant, but it also continues to tilt the scales against the defendant even after the evidence has been produced. A better solution to the problem of access to evidence would shift to the defendant the burden of coming forward with enough evidence to raise the issue, and then leave with the government the ultimate burden of proof after all the evidence is in.

A third proposed criterion for identifying exceptions to the reasonable doubt rule has become the center of a major debate. This controversy raises basic questions about the relationship between substantive law and procedure, as well as about the relationship between state legislatures and the federal Constitution on matters of criminal law. Some commentators have argued that the reasonable doubt rule should not apply to any fact that the legislature could constitutionally have omitted from its substantive criminal law. They argue that if the legislature has the constitutional power to make a fact irrelevant to guilt, then it must also have the power to choose its own rules for proving that fact. Put differently, if the legislature has created a gratuitous defense, then that issue is exempt from the requirement that the government prove its case beyond a reasonable doubt.

Other commentators argue that legislative power to eliminate a defense does not entail the power to shift to the defendant the burden of proof. They maintain that both the practical and the symbolic functions of the reasonable doubt rule apply with full force where a gratuitous defense is concerned.

The controversy is set forth in a pair of articles by Barbara Underwood and by John Jeffries and Paul Stephan. Jeffries and Stephan argue that it is both illogical and unwise to impose strict procedural requirements on the proof of a gratuitous defense. It is illogical, they say, because only if the Constitution requires the state to prove a particular fact as a prerequisite to conviction does the Constitution also require the state to prove that fact beyond a reasonable doubt. It is unwise, they argue, because legislatures have often been willing to enact new defenses to crime only in conjunction with rules that shift the burden of proof to the defendant. To prohibit such compromises, they contend, would stifle criminal law reform.

Underwood argues, by contrast, that the power to eliminate an issue from the criminal law does not entail the power to alter the rules of proof for that issue. In her view, the Constitution allocates to the states very broad power to define the substantive criminal law, but it imposes rigorous procedural requirements on the process of proving whatever facts the state has made criminal. Thus, the Constitution does not permit a state to adopt a controversial defense, and then limit it by shifting the burden of proof to the defendant. Instead, the state must resolve controversies over criminal law policy by making adjustments and compromises in the content of the substantive criminal law.

For example, a state legislature might be divided over a proposal to exempt from the narcotics law those who possess narcotics solely for personal use. A procedural compromise would be to adopt the defense in full, and to limit it by shifting the burden of proof to the defendant. A substantive compromise would be to adopt the defense in part, exempting only those who possess narcotics for personal use in specified small quantities, or in the privacy of the home. If the Constitution prohibits the procedural compromise, then the legislature must adopt or reject the defense or find a substantive compromise.

It is, of course, difficult to determine whether in fact criminal law reform would be stifled if the burden-shifting device were prohibited. Legislatures might instead adopt reforms without burden-shifting, or they might find satisfactory substantive compromises. Moreover, the argument that burden-shifting is necessary for legislative reform does not require an exception from the reasonable doubt rule for all gratuitous defenses. It requires an exception only for those new gratuitous defenses that result from legislative compromise.

Linking the reasonable doubt rule to only those facts that the Court says are constitutionally required to constitute a crime is equally questionable. Commentators have long urged the Court to develop a body of constitutional criminal law, but the Court has been highly reluctant to do so. In Montana v. Egelhoff, 518 U.S. 37 (1996), for instance, the Court struggled with the issue of whether the state could help meet its burden of proving that the defendant had intentionally killed the victim by barring him from showing that he was intoxicated. A bare majority of the Court held that the state could bar the intoxication defense, but it was badly split in its reasoning, and the case's difficulties suggest that the Court rarely will plunge into the quagmire of reviewing state substantive criminal law. Given the paucity of constitutional criminal law, if the rule applies only to constitutionally necessary facts, then it may have almost no application at all (Sundby, 1989a).

Moreover, the gratuitous character of a defense is not by itself sufficient to exempt that defense from other constitutional requirements of fair procedure. Even a defendant raising a gratuitous defense has the right to have that issue determined at a trial by jury, with counsel and confrontation of adverse witnesses. If an issue is exempt from the requirement of proof beyond a reasonable doubt, the reason must not be solely that the defense is gratuitous, but that for some reason it is less important to protect the defendant against error.

Presumptions as burden-shifting devices

Closely related to rules that regulate the burden of proof are rules of law that establish presumptions. These rules come in many variations, but they all instruct the fact finder to infer one fact from evidence that directly proves some other fact.

The Supreme Court has recognized that some forms of presumptions shift the burden of proof to the defendant in an unconstitutional manner. In Sandstrom v. Montana, 442 U.S. 510 (1979), the Court found constitutional error in an instruction that "the law presumes that a person intends the ordinary consequences of his voluntary acts" (p. 513). That instruction, in a prosecution for "deliberate homicide," shifted to the defendant the burden of proving he did not intend to cause death.

By contrast, in County Court v. Allen, 442 U.S. 140 (1979), the Court upheld an instruction that "upon proof of the presence of the machine gun and the hand weapons, you may infer and draw a conclusion that such prohibited weapon was possessed by each of the defendants who occupied the automobile at the time when such instruments were found" (p. 161, n. 20). That instruction, in a prosecution for criminal possession of a weapon, was held to be merely permissive and not burden-shifting, because it left the jury free to credit or reject the inference.

From these and earlier cases, several principles emerge. If the reasonable doubt rule applies to an issue, then the rule cannot constitutionally be circumvented by a presumption. Both the issue of intent in Sandstrom and the issue of possession in County Court were clearly subject to the reasonable doubt rule. For such issues, there can be no mandatory presumptions, even if they are rebuttable, because such presumptions are burden-shifting. The state may, however, use presumptions that merely authorize a permissible inference or invite the fact finder to consider it.

Neither Sandstrom nor County Court dealt with issues outside the scope of the reasonable doubt rule. For such issues there can be no constitutional objection to the burden-shifting character of a presumption, although the Constitution requires that any presumption, whether burden-shifting or not, have some rational basis.

Barbara D. Underwood

Scott E. Sundby

See also Criminal Procedure: Constitutional Aspects; Sentencing: Procedural Protection; Trial, Criminal.


Alexander, Larry. "The Supreme Court, Dr. Jekyll, and the Due Process of Proof." Supreme Court Review 191 (1996): 191217.

Allen, Ronald J. "Structuring Jury Decisionmaking in Criminal Cases: A Unified Constitutional Approach to Evidentiary Devices." Harvard Law Review 94 (1980): 321368.

Dane, Francis C. "In Search of Reasonable Doubt: A Systematic Examination of Selected Quantification Approaches." Law and Human Behavior 9 (1985): 141.

Dripps, Donald A. "The Constitutional Status of the Reasonable Doubt Rule." California Law Review 75 (1987): 1665.

Fletcher, George P. "Two Kinds of Legal Rules: A Comparative Study of Burden-of-Persuasion Practices in Criminal Cases." Yale Law Journal 77 (1968): 880935.

Green, Thomas A. "The Jury and the English Law of Homicide, 12001600." Michigan Law Review 74 (1976): 413499.

Jeffries, John C., Jr., and Stephan, Paul B. "Defenses, Presumptions, and Burden of Proof in the Criminal Law." Yale Law Journal 88 (1979): 13251407.

L.S.E. Jury Project. "Juries and the Rules of Evidence." Criminal Law Review (1973): 208223.

May, John W. "Some Rules of Evidence of Reasonable Doubt in Civil and Criminal Cases." American Law Review 10 (1876): 6.

Morano, Anthony A. "A Reexamination of the Development of the Reasonable Doubt Rule." Boston University Law Review 55 (1975): 507528.

Nesson, Charles R. "Reasonable Doubt and Permissive Inferences: The Value of Complexity." Harvard Law Review 92 (1979): 11871225.

Saltzburg, Stephen A. "Standards of Proof and Preliminary Questions of Fact." Stanford Law Review 27 (1975): 271305.

Schwartz, Louis B. "'Innocence'A Dialogue with Professor Sundby." Hastings Law Journal 41 (1989): 153.

Shapiro, Barbara A. "Beyond a Reasonable Doubt" and "Probable Cause": Historical Perspectives on the Anglo-American Law of Evidence. Berkeley: University of California Press, 1991.

Simon, Rita James. "Judges' Translations of Burdens of Proof into Statements of Probability." Trial Lawyer's Guide (1969): 103114.

. "'Beyond a Reasonable Doubt': An Experimental Attempt at Quantification." Journal of Applied Behavioral Science 6 (1970): 203209.

Simon, Rita James, and Mahan, Linda. "Quantifying Burdens of ProofA View from the Bench, the Jury, and the Classroom." Law and Society Review 5 (1971): 319330.

Sundby, Scott E. "The Reasonable Doubt Rule and the Meaning of Innocence." Hastings Law Journal 40 (1989a): 457.

. "The Virtues of a Procedural View of InnocenceA Response to Professor Schwartz." Hastings Law Journal 41 (1989b): 161.

Underwood, Barbara D. "The Thumb on the Scales of Justice: Burdens of Persuasion in Criminal Cases." Yale Law Journal 86 (1977): 12991348.

Uviller, H. Richard. "Acquitting the Guilty: Two Case Studies on Jury Misgivings and the Misunderstood Standard of Proof." Criminal Law Forum 2 (1990): 1.


Addington v. Texas, 441 U.S. 418 (1979).

Almendarez-Torres v. United States, 523 U.S. 224 (1998).

Apprendi v. New Jersey, 120 S. Ct. 2348 (2000).

County Court v. Allen, 442 U.S. 140 (1979).

In re Winship, 397 U.S. 358 (1970).

Martin v. Ohio, 480 U.S. 228 (1987).

McMillan v. Pennsylvania, 477 U.S. 79 (1986).

Montana v. Egelhoff, 518 U.S. 37 (1996).

Mullaney v. Wilbur, 421 U.S. 684 (1975).

Patterson v. New York, 432 U.S. 197 (1977).

Sandstrom v. Montana, 442 U.S. 510 (1979).

Santosky v. Kramer, 455 U.S. 745 (1982).

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Burden of Proof


A duty placed upon a civil or criminal defendant to prove or disprove a disputed fact.

Burden of proof can define the duty placed upon a party to prove or disprove a disputed fact, or it can define which party bears this burden. In criminal cases, the burden of proof is placed on the prosecution, who must demonstrate that the defendant is guilty before a jury may convict him or her. But in some jurisdiction, the defendant has the burden of establishing the existence of certain facts that give rise to a defense, such as the insanity plea. In civil cases, the plaintiff is normally charged with the burden of proof, but the defendant can be required to establish certain defenses.

Burden of proof can also define the burden of persuasion, or the quantum of proof by which the party with the burden of proof must establish or refute a disputed factual issue. In criminal cases, the prosecution must prove the defendant's guilt beyond a reasonable doubt.

Judges explain the reasonable doubt standard to jurors in a number of ways. Federal jury instructions provide that proof beyond a reasonable doubt is "proof of such a convincing character that a reasonable person would not hesitate to act upon it in the most important of his own affairs." State judges typically describe the standard by telling jurors that they possess a reasonable doubt as to the defendant's guilt if, based on all the evidence in the case, they would be uncomfortable with a criminal conviction. In giving the reasonable doubt instruction, judges regularly remind jurors that a criminal conviction imposes a variety of hardships on a defendant, including public humiliation, incarceration, fines, and occasionally the forfeiture of property. Reasonable doubt is the highest standard of proof used in any judicial proceeding.

Reasonable doubt is also a constitutionally mandated burden of proof in criminal proceedings. The U.S. Supreme Court has ruled that the due process clause of the fifth amendment and Fourteenth Amendments to the federal constitution prohibit criminal defendants from being convicted on any quantum of evidence less than proof beyond a reasonable doubt. in re winship, 397 U.S. 358, 90 S. Ct. 1068, 23 L. Ed. 2D 368 (1970). Although the reasonable doubt standard is not specifically mentioned anywhere in the Constitution, the Court observed that the standard is so deeply rooted in the nation's history as to reflect the fundamental value that "it is far worse to convict an innocent man than to let a guilty man go free."

In civil litigation the standard of proof is either proof by a preponderance of the evidence or proof by clear and convincing evidence. Both are lower burdens of proof than beyond a reasonable doubt. A preponderance of the evidence simply means that one side has more evidence in its favor than the other, even by the smallest degree. Clear and convincing evidence is evidence that establishes the truth of a disputed fact by a high probability. Criminal trials employ a higher standard of proof because criminal defendants often face the deprivation of life or liberty if convicted while civil defendants generally only face an order to pay money damages if the plaintiff prevails.

further readings

Scheibe, Benjamin D. 2003. "Claim of Reverse Engineering Doesn't Alter Burden of Proof." The Los Angeles Daily Journal 116 (October 2).

Twining, William and Stein, Alex, eds. 1992. Evidence and Proof. New York: New York University Press.


Burden of Persuasion; Due Process of Law; Evidence; Fifth Amendment; Fourteenth Amendment; Proof; Reasonable Doubt.

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