It would no doubt be helpful to present a jury with information of how plaintiff was driving too fast in choppy water before being thrown from a boat or how the plaintiff allowed lint to collect in the exhaust duct before a fire in the dryer caused property damage. But, in the product liability context a plaintiff’s conduct is generally irrelevant to the existence of a manufacturing or design defect and evidence of comparative fault doesn't go to the jury unless plaintiff knew his conduct was dangerous in light of the alleged defect. Nonetheless, the Federal District Court in New Jersey Manufacturers Insurance Group v. Electrolux Home Products, Inc., No. 10-civ-1597 (D.N.J., Aug. 20, 2013) found no error in admitting this type of evidence to the extent it is relevant to proximate cause.
In New Jersey Manufacturer's Insurance, a subrogation case, plaintiff sought a new trial after it failed to convince a jury that a clothes dryer was defective or that the dryer was supplied without adequate warnings. Plaintiff asserted several grounds for a new trial, including that it was prejudiced when the defense was allowed to present evidence that the insured failed to maintain the dryer properly. The District of New Jersey held that such evidence may be admitted so long as “a reasonable jury could conclude that the conduct…was the sole proximate cause” of the harm.
Relevance is relative. Evidence is inadmissible where it does not relate to some relevant aspect of the case. The trick, therefore, is in identifying its relevance. The clothes dryer example in New Jersey is useful in making sure the jury learns of a plaintiff's conduct. Where evidence of the plaintiff’s conduct may not be admissible to argue contributory negligence, or relevant to any alleged defect, it is potentially admissible to show plaintiff's conduct was the sole cause of his own injuries.