Products liability is an area of law that deals with personal injury and property damage caused by defective products. Defective products are products that contain a design or manufacturing defect.

Products Liability Lawsuits

If a consumer suffers an injury while using a defective product, he or she can sue the manufacturer or, in some cases, the distributor, seller or retailer of the product. To recover damages in a products liability lawsuit, the consumer must show that the product was defective and that the defective product caused his or her injury or loss. There has to be a direct connection between the product defect and the injury or loss. In legal terms, this is referred to as causation.

Expert Witnesses

Causation is generally shown at trial through the testimony of an expert witness, a witness who has knowledge of a technical subject. Technical experts can give opinions on scientific information that is beyond the general knowledge of the jurors. Because of his or her education, training or experience, an expert witness's testimony helps the jury understand complex technical issues. Scientific methodology is based on coming up with a supposition or premise and testing it to see if experiments support the supposition. If they do, the supposition is regarded as a valid scientific theory.

'Junk Science'

Product liability cases in the 1980s and early 1990s were characterized by the battle of the experts. Experts for both sides presented opinions that contradicted one another, leaving the jury to pick between the experts. It appeared that expert testimony was increasingly based on what some came to call "junk science." Junk science refers to novel scientific theories that are based on biased data or inferences that are not scientifically proven.

Daubert Test or Standard for Expert Testimony

In 1993, the United States Supreme Court established principles for the admission of expert testimony in the landmark case Daubert v. Merrell Dow Pharmaceuticals. The court stated that trial judges should act as gatekeepers and keep out testimony based on junk science and held that scientific evidence had to be both relevant and reliable. The court listed four standards for admitting scientific evidence:

1. Has the theory been tested?
   
2. Has the theory been subjected to peer review and publication?
   
3. What is the known or potential rate of error and are there controlling standards?
   
4. Does the scientific community generally accept the theory?

The trial court must apply these standards in deciding whether to admit expert testimony.

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