The term "reasonable doubt" is difficult to define with precision. Indeed, while the jury must always be instructed to apply this standard when determining guilt or innocence, less agreement exists on whether the Court should define reasonable doubt for the jury. Some state and federal courts have concluded that jury instructions defining reasonable doubt are not required and should be avoided, although it is not usually per se reversible error for the trial court to give an accurate instruction defining the term. Most of these courts have reached the conclusion that reasonable doubt need not be defined on the grounds that the term is self-explanatory, and a definition would tend only to confuse the jury. Other courts, however, require that juries receive a definition of reasonable doubt,particularly when the jury requests an instruction.
For those courts that still define the term, the Supreme Court has made it clear that the trial court must be careful what definition it uses. For example, in Cage v. Louisiana,a prosecution for murder, a jury instruction defined "reasonable doubt" in part as follows: "This doubt, however, must be a reasonable one; that is one that is founded upon a real tangible substantial basis and not upon mere caprice and conjecture. It must be such doubt as would give rise to a grave uncertainty, raised in your mind by reasons of the unsatisfactory character of the evidence or lack thereof. A reasonable doubt is not a mere possible doubt. It is an actual substantial doubt. It is a doubt that a reasonable man can seriously entertain. What is required is not an absolute or mathematical certainty, but a moral certainty." In ruling that the instruction was contrary to the "beyond a reasonable doubt" requirement articulated in Winship, the Court explained: "In construing the instruction, we consider how reasonable jurors could have understood the charge as a whole
. The charge did at one point instruct that to convict, guilt must be found beyond a reasonable doubt, but it then equated a reasonable doubt with a 'grave uncertainty' and an 'actual substantial doubt,' and stated that what was required was a 'moral certainty' that the defendant was guilty. It is plain to us that the words 'substantial' and 'grave,' as they are commonly understood, suggest a higher degree of doubt than is required for acquittal under the reasonable doubt standard. When those statements are then considered with the reference to 'moral certainty', rather than evidentiary certainty, it becomes clear that a reasonable juror could have interpreted the instruction to allow a finding of guilt based on a degree of proof below that required by the Due Process Clause."
Some courts prefer to define reasonable doubt in terms of hesitation to act (i.e., the kind of doubt that would make a reasonable person hesitate or pause to act in important life transactions), rather than a willingness to act (i.e., the kind of doubt that would make a reasonable person willing to act in important life transactions). Some federal authorities have criticized the "hesitate" language. Some courts have also admonished trial courts not to use phrases such as "equally balanced mind," "probabilities," or "balancing of evidence" when defining the term reasonable doubt. Some courts have defined reasonable doubt using the phrase "firmly convinced" and other courts have used the phrase "abiding conviction" to define reasonable doubt.
In some cases, the attempt has been made to define the phrase in terms of itself, i.e., a reasonable doubt is a doubt for which a reason can be given. Some courts have criticized this definition as requiring a juror to vote for conviction, in spite of a "reasonable" doubt of guilt, if the juror cannot verbalize a particular reason for the doubt.
A reasonable doubt must be a doubt arising from the evidence, or from the want of evidence, and cannot be an imaginary doubt or conjecture unrelated to the evidence.
In some states, particularly where the only evidence is circumstantial, proof beyond a reasonable doubt must exclude every reasonable hypothesis or inference except guilt.* However, a proper reasonable doubt instruction has been held to be sufficient even in a circumstantial evidence case. In no event is it necessary to dispel all possible doubt. It is not necessary to show that the defendant is probably innocent, for a distinction exists between a probability of innocence and a reasonable doubt of guilt. The evidence may leave in the minds of the jurors a reasonable doubt, even though it is not sufficient to show a probability of innocence.
