Where an expert’s hypothesis was untested, his testimony was properly excluded as unreliable.
“Mizen made no attempt to test his hypothesis. Bielskis suggests that this inquiry is unnecessary because Mizen needed nothing more than his engineering background and experience to conclude that the caster stem collapsed on account of a brittle fracture brought on by overtightening. But that theory is certainly capable of being tested. Mizen reached his conclusion by examining the broken scaffold for approximately an hour with his naked eye. He did not take the time to measure the caster stem: indeed, he assumed in his report that the caster stem was 3/8” and only later discovered that it was in fact ½.” He admitted in his deposition that he had no idea what alloy was used to construct the caster stem and that he had made no effort to quantify its tensile strength or yield strength.”
10-1194 Bielskis v. Louisville Ladder, Inc.
Appeal from the United States District Court for the Northern District of Illinois, Leinenweber, J., Rovner, J.