Weight of evidence is a legal term used when gauging the sufficiency of proof that is presented in a legal dispute. For this method of analysis to work, it is necessary to consider the evidence from the opposing parties and to compare them. This comparison should lead to a decision of which party appears to have the strongest case. The party that lacks the weight of evidence, therefore, should be the party the court rules against.
In a court case, there are at least two parties. The prosecution generally is supposed to bear the burden of proving the guilt of the defendant. Both parties, however, are likely to submit evidence to support their claims. This could lead a person to falsely assume that the party that presents the most evidence will be the one whose case has the greatest weight and thereby the winner.
One reason that more evidence does not necessarily result in a favorable outcome is that some evidence is not necessarily true, some will be deemed inadmissible, and sometimes verification of proof is unavailable to determine the truth of the evidence. It is important to remember that evidence is merely material, sometimes oral and sometimes physical, which is provided in an attempt to convince the trier of fact, which is generally a judge, jury, or magistrate.
It is the legal responsibility of these individuals to assess the evidence provided and to determine what is relevant and what is believable. Another assumption that should not be made when trying to understand the principles of weight of evidence is that all evidence must be verified. Sometimes verification is not possible but the trier of fact may still find the evidence believable. This means that it will count in favor of the party that presented it.
Although the jury may find some evidence believable even when it lacks concrete support, this does not mean it is given a higher value than evidence that can be confirmed. When considering weight of evidence, some items can weigh more heavily than others. For example, a photograph may carry heavier weight than an unverified oral testimony although the trier of fact is inclined to believe both. One of the difficulties of being a trier of fact is that each side may have some evidence that weighs in favor of their arguments. The side whose overall presentation of evidence is most convincing can be said to possess the weight of evidence and, therefore, should win the case.