The preponderance of the evidence is the burden of proof standard in most civil and tort cases. To demonstrate a preponderance of the evidence, and thereby win a civil case, a plaintiff must convince a trier of fact that the defendant is more likely than not to be liable for the plaintiff's damages. In other words, that there is a greater than 50 percent chance that the events occurred as the plaintiff alleges.

The preponderance standard differs from the beyond a reasonable doubt standard in criminal cases, where a jury must be convinced there is no other reasonable explanation for the crimes. In the late 1700s, lawyers and legal theorists began to question if civil cases, in the name of justice, really merited such a high burden as beyond reasonable doubt. In an 1801 criminal case in Delaware, State v. Crocker, a judge instructed the jury:

Presumptive evidence, where there is a concurrence of circumstances convincing the jury, is sufficient. In civil cases a preponderance of evidence is sufficient for you to convict; in criminal, you should have proof.

Previously, jurors were told to "give a verdict as your consciences direct you," or base their judgment on what they "think" or "believe." After the preponderance standard was introduce in the late 1700s, the idea slowly picked up steam and became the law of the land for civil cases. As the Pennsylvania summarized in Karch v. Karch, 885 A.2d 535 (2005):

preponderance of the evidence is defined as the greater weight of the evidence, i.e., to tip a scale slightly is the criteria or requirement for preponderance of the evidence.

For example, in a car accident claim, you would only need to convince the jury, judge or mediator that the other party probably caused your injuries. This can be achieved through photographs, eye witness depositions, police reports and testimony from expert witnesses. In a slip and fall case, the fact finder would need to believe that the property owner likely should have known of the dangerous condition that injured you.