What Does Proof Beyond a Reasonable Doubt Mean?

Why the Guilty Sometimes Go Free and Why That's Not Always a Bad Thing

Jurors and visitors listening to testimony in the OJ Simpson trial
Jurors Hear Testimony in Murder Trial of O.J. Simpson. David Hume Kennerly / Getty Images

In the United States court system, the fair and impartial delivery of justice is based on two fundamental tenets: That all persons accused of crimes are considered to be innocent until proven guilty, and that their guilt must be proven “beyond a reasonable doubt.”

While the requirement that guilt must be proven beyond a reasonable doubt is meant to protect the rights of Americans charged with crimes, it often leaves juries with the momentous task of answering the often subjective question — how much doubt is “reasonable doubt?”

Constitutional Basis for "Beyond a Reasonable Doubt"

Under the Due Process clauses of the Fifth and Fourteenth Amendments to the U.S. Constitution, persons accused of crimes are protected from “conviction except upon proof beyond a reasonable doubt of every fact necessary to constitute the crime with which he is charged.”

The U.S. Supreme Court first acknowledged the concept in its decision on the 1880 case of Miles v. United States: “The evidence upon which a jury is justified in returning a verdict of guilty must be sufficient to produce a conviction of guilt, to the exclusion of all reasonable doubt.”

While judges are required to instruct juries to apply the reasonable doubt standard, legal experts disagree on whether the jury should also be given a quantifiable definition of “reasonable doubt.” In the 1994 case of Victor v. Nebraska, the Supreme Court ruled that the reasonable doubt instructions given to juries must be clear, but declined to specify a standard set of such instructions.

As a result of Victor v. Nebraska ruling, the various courts have created their own reasonable doubt instructions.

For example, judges of the Ninth U.S. Circuit Court of Appeals instruct juries that, “A reasonable doubt is a doubt based upon reason and common sense and is not based purely on speculation.

It may arise from a careful and impartial consideration of all the evidence, or from lack of evidence.”

Considering the Quality of Evidence

As part of their “careful and impartial consideration” of evidence presented during the trial, jurors must also evaluate the quality of that evidence.

While first-hand evidence such as eyewitness testimony, surveillance tapes, and DNA matching help eliminate doubts of guilt, jurors assume — and are typically reminded by defense attorneys — that witness may lie, photographic evidence can be faked, and DNA samples can become tainted or mishandled. Short of voluntary or legally-obtained confessions, most evidence is open to being challenged as invalid or circumstantial, thus helping to establish “reasonable doubt” in the minds of the jurors.

"Reasonable" Does Not Mean "All"

As in most other criminal courts, the Ninth U.S. Circuit Court also instructs jurors that proof beyond a reasonable doubt is a doubt that leaves them “firmly convinced” that the defendant is guilty.

Perhaps most importantly, jurors in all courts are instructed that beyond a “reasonable” doubt does not mean beyond “all” doubt. As Ninth Circuit judges state it, “It is not required that the government (the prosecution) proves guilt beyond all possible doubt.”

Finally, judges instruct jurors that after their “careful and impartial” consideration of the evidence they have seen, they are not convinced beyond a reasonable doubt that the defendant actually committed the crime as charged, it is their duty as jurors to find the defendant not guilty.

Can "Reasonable" Be Quantified?

Is it even possible to assign a definite numeric value to such a subjective, opinion-driven concept as reasonable doubt?

Over the years, legal authorities have generally agreed that proof “beyond a reasonable doubt” requires jurors to be at least 98% to 99% certain that the evidence proves the defendant to be guilty.

This is in contrast to civil trials on lawsuits, in which a lower standard of proof, known as a “preponderance of the evidence” is required. In civil trials, a party might prevail with little as 51% probability that events involved actually occurred as claimed.

This rather wide discrepancy in the standard of proof required can be best explained by the fact that persons found guilty in criminal trials face far more severe potential punishment — from jail time to death — compared to the monetary penalties typically involved in civil trials. In general, defendants in criminal trials are afforded more constitutionally-ensured protections than defendants in civil trials. 

The "Reasonable Person" Element

In criminal trials, jurors are often instructed to decide whether the defendant is guilty or not by applying an objective test in which the defendant’s actions are compared to those of a “reasonable person” acting under similar circumstances. Basically, would any other reasonable person have done the same things the defendant did?

This “reasonable person” test is often applied in trials involving so-called “stand your ground” or “castle doctrine” laws that justify the use of deadly force in acts of self-defense. For example, would a reasonable person have also chosen to shoot his or her attacker under the same circumstances or not?

Of course, such a “reasonable” person is little more than a fictional ideal based on the individual juror’s opinion of how a “typical” person, possessing ordinary knowledge and prudence, would act in certain circumstances.

According to this standard, most jurors naturally tend to consider themselves to be reasonable people and thus judge the defendant’s conduct from a viewpoint of, “What would I have done?”

Since the test of whether a person has acted as a reasonable person is an objective one, it does not take into account the particular abilities of the defendant.

As a result, defendants who have shown a low level of intelligence or have habitually acted carelessly are held to the same standards of conduct as more intelligent or careful persons, or as the ancient legal principle holds, “Ignorance of the law excuses no one.”

Why the Guilty Sometimes Go Free

If all persons accused of crimes must be considered innocent until proven guilty beyond a "reasonable doubt," and that even the slightest degree of doubt can sway even a "reasonable person’s" opinion of a defendant’s guilt, doesn’t the American criminal justice system occasionally allow guilty people to go free?

Indeed it does, but this is entirely by design. In crafting the various provisions of the Constitution protecting rights of the accused, the Framers felt it essential that America apply the same standard of justice expressed by renowned English jurist William Blackstone in his often-cited 1760s work, Commentaries on the Laws of England, “It is better that ten guilty persons escape than that one innocent suffer.”

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Longley, Robert. "What Does Proof Beyond a Reasonable Doubt Mean?" ThoughtCo, Apr. 20, 2018, thoughtco.com/proof-beyond-a-reasonable-doubt-definition-4156891. Longley, Robert. (2018, April 20). What Does Proof Beyond a Reasonable Doubt Mean? Retrieved from https://www.thoughtco.com/proof-beyond-a-reasonable-doubt-definition-4156891 Longley, Robert. "What Does Proof Beyond a Reasonable Doubt Mean?" ThoughtCo. https://www.thoughtco.com/proof-beyond-a-reasonable-doubt-definition-4156891 (accessed May 26, 2018).