Plaintiff suffered no prejudice from the exclusion of evidence of knowledge of risks and effective alternatives on the part of the device manufacturer, since none of the evidence excluded addressed causation, an element of the claim.
If the admission of expert testimony on operating room airflow was error, it was harmless, given the many other avenues established for the bacteria to have entered the wound.
As causation is an element of a lack of warning claim under state law, if the court erred in holding that the deft had actual or constructive knowledge, the error was harmless, since causation was never established.