The court will generally not allow opinion testimony with lay witnesses during a car accident case when the matter pertains to a specialized matter, like an injury or a matter concerning the inner workings of the car. A layperson is defined as meaning someone who does not have the expertise necessary to be considered appropriate for a trial. An expert witness has special training and experience and is allowed to give opinion testimony, such as a medical doctor.
In a personal injury case, the plaintiff has the burden of proving that the at-fault party was negligent and violated a standard of care that was expected of them, that the plaintiff suffered injury, and that the injury was caused by the negligence of the at-fault party.