Forensic testimony is testimony which is given by an expert witness who offers information which can shed additional light on the nature of a crime, the processes used to investigate it, and the factors which might surround the situation. Expert witnesses can testify for the prosecution and the defense, and it is conventional to compensate them for their time in the stand, as a recognition of the fact that they are not simply testifying, but also providing professional services. Lawyers can solicit forensic testimony in a wide variety of cases, from murders where the time of death is in dispute, to civil suits where an attempt is being made to prove negligence.
The word “forensic” is often associated in the public mind with crime scene investigation. In fact, the word really means “pertaining to a legal trial,” and it is used to refer to materials used in conjunction with a trial, including witnesses and evidence. While forensic testimony can include testimony from coroners and crime scene investigators, it is just as likely to include testimony from psychologists, economists, accident reconstruction specialists, and engineers.
The first step in forensic testimony usually involves the establishment of the credentials of the person who is testifying. Especially when a trial may involve competing forensic witnesses, both sides want to present their witness in the best possible light, and want to suggest that their witness is the most reliable. Credentials include things like the job the witness performs, the number of years of experience the witness has, and the number of publications the witness has made. Someone like the head of the forensic anthropology department at a major university with 30 years of experience and dozens of publications in books and scientific journals may be deemed more reliable, for example, than a deputy medical examiner with three years of experience who works in a small lab.
After establishing credentials, questions relevant to the case can be asked. For example, if a forensic engineer is testifying, he or she will be asked questions about the incident the trial revolves around. If the prosecution would like to demonstrate, for instance, that a poor weld led to metal fatigue, causing someone to die, the engineer would be asked about the quality of the weld, the metals used in construction, and the standards for the industry. The expert's testimony is used to provide a more complete picture of the events being discussed in court.
This type of testimony can be critical to a case. Getting the opinion of an expert can sometimes literally make or break a case. For example, forensic testimony might be able to show that someone acted in a way which is inconsistent with industry standards, demonstrating that neglect occurred and proving the case for one side or the other. However, it is important to be aware that experts can conflict, and two witnesses may come up with very different interpretations of the evidence and events.