The Court of Appeals for the Tenth Circuit held that it was not error for the Court to instruct the jury that the defendant could not be held liable if a product was substantially changed before the accident even though there was no evidence that the change was intentional. In Martinez v. Caterpillar Inc., 572 F.3d 1129 (10th Cir. 2009) a tire on a motor grader manufactured by the defendant deflated due to an impact with a rock. Plaintiff was attempting to inflate the tire when the wheel assembly exploded causing substantial injuries. After the accident a lock ring, part of the wheel assembly, was found about 20 feet away. An expert testified that the wheel assembly would not have separated had the lock ring been in place and that the impact which caused the tire to deflate could have knocked the lock ring loose.
Plaintiff, based on an Eleventh Circuit decision that a substantial change only occurs if an entity other than the product seller changes the design construction or the formula of the product, contended that there was not a substantial change because it occurred during the normal, intended use of the product, such as driving the motor grader. The Court of Appeals disagreed and in holding that it was proper to give the instruction said,
Thus, in determining whether a product underwent a substantial change, the analysis focuses on the product’s condition when it left the manufacturer’s control and its condition at the time of the injury. The analysis does not focus on the way in which the product was changed.