While most witnesses in a trial provide first-hand testimony, expert witnesses are called to provide an informed opinion based on their specialized knowledge, skill, training or education. They can clarify disputed or unclear questions of fact, or simply increase understanding of subjects outside the life experience of ordinary judges or jurors.
The areas of expertise for these witnesses can vary greatly based on the needs of the case. Ballistics experts, handwriting experts, fire investigators, scientists, medical professionals, mechanics and engineers are just a few of the expert witnesses who may be called to support the prosecution or defense in a criminal trial. Among the most common types of scientific witnesses are forensic scientists who might be a specialist in fields such as anthropology, archaeology, chemistry or computer science.
A recent real-world example, as reported in The Logan Daily News, is a Chillicothe, Ohio murder trial in which the prosecution called expert witnesses including:
A former FBI agent, called to testify about the route logged into the GPS over a specific time period to see where the vehicle had traveled and when
A forensic scientist with the Ohio Bureau of Criminal Investigation, who testified about DNA analysis of several items of evidence including a ball cap, a cell phone, Mountain Dew bottle, cigarette butt, septic tank lid and screws, and zip ties
A forensic scientist with the Montgomery County Coroner’s Office, who testified about the condition of the victim’s body upon arrival at his office in Dayton
When clients face criminal charges, expert testimony is sometimes arranged by defense attorneys – and experts are compensated. In some cases experts are paid by a public entity such as the court or the prosecutor. When it makes the difference in a key trial, expert witness money is well spent.