(Tex., Civil Procedure, Evidence, Injury And Tort Law) In plaintiffs' wrongful death and survival claims against Wal-Mart for the death of their son from smoke inhalation, claiming that a halogen lamp purchased from Wal-Mart caused the fire, the court of appeals' reversal of the trial court's grant of defendant's motion for summary judgment on the ground that plaintiffs produced evidence on each challenged element of their cause of action is reversed as, plaintiff's expert's testimony was legally insufficient to support causation.