Holding that after a defendant identifies a plausible alternative cause, it is "necessary for the plaintiffs expert to offer a good explanation as to why his or her conclusion remains reliable"
Holding that “a defendant who seeks the admission of expert testimony must make an on-the-record detailed proffer to the court, including an explanation of precisely how the expert's testimony is relevant to the [issues in dispute]”
Holding that the district court erred in finding that a treating physician was not qualified to render a diagnosis because he was not a pathologist or oncologist and relied on a pathology report prepared by someone else
Holding " party confronted with an adverse expert witness who has sufficient, though perhaps not overwhelming, facts and assumptions as the basis for his opinion can highlight those weaknesses through effective cross-examination"