Expert testimony can make or break the likelihood a jury verdict will survive an appeal, especially when causation is disputed in a products liability case. But as recent opinions show, appellate courts can differ on when expert testimony is needed to prove causation — and when it isn’t.

In June, the Texas Supreme Court vacated a jury award because of the lack of expert testimony on causation, but earlier this month the 5th U.S. Circuit Court of Appeals affirmed a verdict in a similar case.