I often hear questions from other lawyers about demonstrative evidence and how it can be used in court. What is demonstrative evidence? Simply stated, demonstrative evidence is not an acutal depiction of a fact or event from the underlying action. Instead, it is a depiction of that fact or event. It could be created specifically for the litigation or it could have already existed.
The foundational requirement to gain admission of demonstrative evidence includes a competent witness (usually an expert who is allowed to state an opinion) to testify that the evidnce accurately represents what it purports to portray and that it would be helpful to the jury in understanding that fact or event.
For example, if a doctor wants to explain how a heart attack occurs, it may be helpful to have an illustration of the arteries that supply blood to the heart and show how a plaque rupture and clots restrict the supply of blood to the heart, eventually leading to destruciton of the heart muscle. In this scenario, the expert need to exhibit familiarity with the illustration and be able to state that the illustration accurately depicts the event of a heart attack. If the other party objects to admission, the judge may give a curative instruction that the illustration is not an actual illustration of the patient's heart, but is admitted for the limited purpose of helping the jury understand how a heart attack occurs.
Using demonstrative evidence may greatly increase the effectiveness of your trial presentation because many jurors will be visual learners and it also can break up the tedium of long and complex testimony.
In addition to medical illustrations, you may also want to consider use of video illustrations, graphical depicitions of data, and timelines. There are several commercially available softwares to help with the creation of these items.