Like a referee checking whether a measuring tool is reliable before letting it decide the score, a court may screen an expert's methods before the expert is allowed to influence a case. A Daubert challenge is a request to exclude or limit expert testimony on the ground that the expert's opinions are not based on reliable methods, sufficient facts, or a proper fit with the issues being decided. It usually targets specialists such as engineers, doctors, accident reconstructionists, or product designers.

In practice, this matters when a case depends on technical opinions. In a product liability claim, one side may offer an expert who says a machine, tire, drug, or safety device was defectively designed. The other side may file a Daubert challenge arguing the testing was weak, the theory was not generally accepted, or the expert jumped from data to conclusions without a sound basis. If the court agrees, that opinion may be kept from the jury.

That can change the value and direction of an injury claim. A plaintiff may need expert proof to show causation, a design defect, or a safer alternative design. In Connecticut, courts apply a closely related reliability standard under State v. Porter (1997) and Connecticut Code of Evidence § 7-2, often described as Porter/Daubert-style review. If key expert evidence is excluded, settlement leverage and trial chances can shift sharply.