A word describing evidence that persuades a judge or jury to lean to one side as opposed to the other during the course of litigation.
In many states, criminal trials require evidence beyond a reasonable doubt.
But in civil trials, evidence is required only by preponderance of the evidence.
The judge (or jury, where applicable) will perceive the evidence of one side as outweighing the other based on which side has the most persuasive or impressive evidence.
The strength or "weight" of evidence is not decided by the sheer number of witnesses because the judge decides on the credibility of witnesses and give their testimony weight accordingly.
The side with the preponderance of evidence wins the civil case but a tie goes to the defendant.
In Smith v Smith, a 1952 Supreme Court of Canada case, it was stated that:
"(C)ivil cases may be proved by a preponderance of evidence or that a finding in such cases may be made upon the basis of a preponderance of probability and I do not propose to attempt a more precise statement of the rule. I wish, however, to emphasize that in every civil action before the tribunal can safely find the affirmative of an issue of fact required to be proved it must be reasonably satisfied, and that whether or not it will be so satisfied must depend upon the totality of the circumstances on which its judgment is formed including the gravity of the consequences of the finding."
Sopinka in The Law of Evidence in Canada (at p. 155), summarized by saying that:
"Simply put, the (judge) must find that the existence of the contested fact is more probable than its nonexistence".