Preponderance of evidence is a standard of proof used in many civil trials. The plaintiff has the burden of proof in such trials, and is required to prove under the preponderance of evidence standard that the events under discussion probably occurred as described. The facts of the case presented must be more convincing than the counterarguments presented by the opposing side. This is the lowest standard of proof and is generally not seen in criminal cases, where the stakes are much higher.
If someone files a claim and the respondent files a counterclaim, the burden of proof shifts to the respondent. Essentially, the person making an assertion about the need for a legal remedy is required to provide proof to back up the assertion and support the case. The plaintiff's information must be most likely true, as presented in court, and the defendant or respondent may be able to win the case by poking enough holes in the claim that it does not appear to be reasonably truthful.
Under the preponderance of evidence standard, the evidence presented must still have legal standing and integrity. While the standards for evidence in civil cases are much lower, people can be penalized for falsifying evidence and testifying incorrectly on the stand. The respondent has an opportunity to examine evidence to confirm its validity and can cross-examine people on the stand to collect more information. These legal rights in court allow people charged with civil or criminal crimes an opportunity to explore the basis of the charges and challenge them in front of the judge.
Plaintiffs attempt to demonstrate that the situation occurred more or less as they claim it did, and to show how their explanation for a series of events is the most likely one. For example, someone could sue for replacement of a broken window, saying a baseball flew through the window and when the person looked out, a person was standing outside with a catcher's glove. Even if no one witnessed the ball going through the window, the preponderance of evidence would seem to indicate the guilt of the person wearing the glove.
A slightly higher standard than the preponderance of evidence, known as clear and convincing evidence, requires people to not just demonstrate that something probably occurred as stated, but to show that the likelihood is very high. Under this standard, the facts of the case must appear demonstrably true. This higher standard is used in both civil and criminal cases when a judge feels it is merited. Finally, for serious criminal cases, people must prove beyond a reasonable doubt that the facts of the case occurred as stated.