Two major types of court witnesses are so-called fact witnesses and expert witnesses. You might sometimes hear fact witnesses referred to as eyewitnesses or percipient witnesses. Fact witnesses will usually testify about things they experienced, things they saw and the things they heard. But a fact witness can usually not give an opinion about a topic that requires special knowledge or special education.
However, an expert witness may testify as to her opinion. A financial expert witness can be an expert based on her knowledge, skill, training, education and experience. An expert’s opinion must be based upon sufficient facts or data and reliable principles or methods.
Expert Witness Vs Fact Witness
Imagine there’s a shooting. People who saw or heard the shooting might have relevant information. For example, a witness could testify as to what the victim was doing before the shooting. A fact witness could probably testify as to how many shots, but what if the fact witness is asked to testify as to the muzzle velocity of a pistol or if the witness is asked about the path of a bullet? This witness probably can’t answer the questions because he’s not an expert.
Using an Expert Witness
Answering these questions requires special knowledge, education or training. Only an expert in forensic science or ballistics would be allowed to answer questions about the path of a bullet. So as a first step, the witness must demonstrate that she has the necessary qualifications as an expert. If she has the qualifications of an expert, she may be allowed to give her opinion provided the opinion is based on sufficient facts or data and sound principles or methods.
Basically, any person can be a fact witness provided they had first-hand access to the matter being deliberated upon. But only a select few people possess the necessary qualifications to offer expert witness services.