The essential things that have to be proved by a plaintiff in a products liability action against the manufacturer or seller of a car or truck are that the vehicle contained a defect that created an unreasonable risk of danger when the vehicle was used for its intended purpose and that the alleged defect caused the occurrence of a collision or similar incident, for example a vehicle fire, that resulted in the death, personal injury, or property damage for which the plaintiff seeks to recover damages. Such alleged defects in a vehicle may include shortcomings in its design, errors in the manufacturing of its numerous parts and their assembly into a complete car or truck, or failure to properly warn the purchaser or user of some danger inherent in the operation and use of the vehicle.

While manufacturing defects, a term that is here meant to encompass mistakes both in the manufacture of the thousands of individual parts that go into a car or truck and in their final assembly into a complete vehicle, are in one way susceptible of fairly direct proof, a number of difficulties stand in the way of proving such a case. If a part is designed to be configured in a certain way, or the connection between two parts is supposed to be made in a certain way, and the allegedly defective part taken from the vehicle involved in the case is configured in a different way or the connection between parts is shown to be other than as designed, it can be argued that the part or assembly that was put into the suspect vehicle was indeed defective. (It should be noted that the condition of a part after an accident is not conclusive proof of its condition before the accident took place.) The manner in which the manufacturing or assembly defect led to a failure in the vehicle’s normal operation that caused the accident or other incident, however, will still have to be proved. And in many cases, particularly those arising out of serious accidents that result in major vehicle damage, the car or truck involved will have been disposed of and the parts will not be available for inspection or as evidence in court, leaving the proof in the case to be based on the competing opinions of expert witnesses about what aspect of a vehicle and its performance might have been the cause of an accident.

Products liability law in the United States, including automotive products liability law, has grown and developed over more than half a century under the separate legal systems of each of the states rather than as a single unified body of federal law. (The National Highway Traffic Safety Administration, popularly known as NHTSA, has enacted a body of Federal Motor Vehicle Safety Standards, or FMVSS, with which every new motor vehicle has to comply, and these federal regulations may have some bearing on a products liability action.) While the principles of products liability law in the different states contain many similarities, the legal standards applied in automotive products liability actions involving claims of manufacturing defects will vary from state to state.