Demonstrative evidence is evidence presented at trial that is not the actual thing, but represents the actual thing. Demonstrative evidence is used to illustrate or clarify witness testimony. Examples of this type of evidence include photographs, videotapes, models, maps, graphs, computer graphics and animations. To admit demonstrative evidence at trial, the lawyer (introducing the evidence) must call a competent witness—one having first-hand knowledge of the actual thing at the relevant dates—to testify that the exhibit (demonstrative evidence) fairly represents or shows the actual thing. To be relevant, the exhibit must help the jury understand some fact of consequence to the case.