Plaintiffs, defendants and prosecutors all use witnesses in both civil and criminal cases. Witnesses can help determine a party’s guilt, assist a judge in sentencing or help the court understand the nuances of facts in complex cases involving technical or highly complex issues. Regardless of which party calls a witness, all parties to the case have the chance to question and cross-examine her to assess her understanding of the case and her credibility.
Witnesses of Material Fact
Witnesses who attest to particular facts are the most common. They are generally lay witnesses, or persons without particular expertise in their field. They can testify only to facts and limited opinions. For example, in a traffic court matter, the police officer who issued the citation will typically appear to give his account of what happened. Likewise, if an individual witnessed a crime in progress -- such as an assault -- she may appear in court to testify to the alleged criminal activity that she saw. Eyewitnesses testify about things they observed firsthand. Some parties may act as witnesses when they have not observed situations directly, but have information related to the case. For example, in a child custody case, a teacher or school counselor might serve as a witness and present documentation about a child’s attendance or grades.
Both civil and criminal trials may use expert witnesses. These witnesses are professionals in their fields who may not be directly related to the case, but have in-depth knowledge about the legal matter in question. For example, in a medical malpractice case, an experienced surgeon might testify on appropriate procedures used in surgery. In a child custody case, a psychologist may testify to the effects of certain types of parental behavior on the child’s well-being. Expert witnesses speak to facts that the average judge, attorney, jury or layperson may not know.
Character witnesses testify about the character of the individual on trial. For example, in the sentencing portion of a criminal trial, a defendant’s boss or a respected member of the community may speak on the defendant's behalf and relate what he has observed about his demeanor and actions. Character witnesses are usually used by the defense to show that the accused person is of good moral character and either would not be inclined to commit the crime in question because he has not shown a pattern of immorality or law-breaking behavior. These persons may be laypersons, such as a long-time colleague, or experts, such as the party’s therapist.
Friendly versus Hostile Witnesses
Because any party to a lawsuit can call witnesses, some witnesses will be favorable to one party's case and harmful to the other party's case. It's often helpful for each party and her lawyer to know what witnesses the opposing party has asked to appear so they can anticipate what types of testimony the witnesses might give and how that testimony will affect their case. In most cases, both parties have to provide witness lists so everyone knows who will appear as witnesses at the trial. As part of discovery -- the information-collecting process of a lawsuit -- either party can usually depose the other party's witnesses, asking them questions under oath before trial to get a feeling for how a witness is likely to answer questions later in court.