Evidence consists of the testimony of witnesses and exhibits which the court allows into evidence. All evidence must be legally admissible. Complex rules of evidence govern what is legally admissible, and disputes between the attorneys are resolved by the trial judge. These evidentiary rulings are important because they help determine what the jury will consider in arriving at their verdict, and errors by the judge in his or her ruling on evidence questions may provide the basis for a later appeal of the verdict. There are two basic types of evidence which can be presented.
Testimony is oral evidence on any relevant matter given by a witness who is under oath.
Physical evidence includes all other types of evidence such as medical records, x-rays, tax returns, and photographs which the trial judge allows the jury to consider. In order to support their position, each side calls witnesses to testify. They may be either lay or expert witnesses. Lay witness may have knowledge of relevant facts, such as an eyewitness to an accident or a spouse who testifies to plaintiff's physical limitations from the accident. A witness who has knowledge or special training not generally known by the general public would be considered an expert witness .