The weight of evidence is the review of all of the evidence in a trial as a whole for the purpose of determining guilt or innocence. There are different types of evidence including direct and circumstantial. When there is no direct evidence in a case there can be a conviction made on the basis of the circumstantial evidence. Where several pieces of evidence are included in a case or trial, they are taken as a whole and considered; the weight of evidence is considered as either in favor of or against conviction.
A famous case using weight of evidence was the OJ Simpson trial. There was no direct evidence, but instead an accumulation of individual pieces of evidence was used in an attempt to prove Simpson's guilt. In that trial, the jury ruled that the weight of evidence was not such to convict. In any case where there is a jury, the jury must consider each piece of evidence in particular and as a whole to determine their vote.