This standard of proof is used exclusively in criminal cases, and a person cannot be convicted of a crime unless a judge or jury is convinced of the defendant’s guilt beyond a reasonable doubt. Precisely, if there is any reasonable uncertainty of guilt, based on the evidence presented, a defendant cannot be convicted.
Ostensibly, this burden requires that a trier of fact (judge, jury, arbiter) is fully satisfied and entirely convinced to a moral certainty that the evidence presented proves the guilt of the defendant. There is essentially no room for wavering or uncertainty; the trier of fact believes the evidence to be precise, indubitable, and leaves one with an inescapable conclusion of certainty. Whereas, in a civil trial, a party may prevail with as little as 51 percent probability (a preponderance), those legal authorities who venture to assign a numerical value to “beyond a reasonable doubt” place it in the certainty range of 98 or 99 percent.
In a criminal trial, the state must prove that the defendant is guilty, and the burden of proof is always with the state for the case in chief. The defendant, carrying a presumption of innocence, has no burden of proof, and need prove nothing. A defendant may sit mute at a criminal trial, because the state has the burden of proof to show that the defendant satisfied each element of the statutory definition of a crime by his or her action/participation or failure to act. Any evidence offered by the defense is generally directed toward discrediting or undermining the state’s evidence, and does not contribute to any evidentiary burden.
However, if a defendant initiates to offer a defense to the jury, such as a defense of insanity, the burden technically shifts to the defendant to prove insanity and avoid a verdict of guilt. Likewise, a defendant claiming self-defense or duress carries the burden of proof to establish all elements of those defenses to either avoid or mitigate a guilty verdict.