In Casteel, Columbia Rio Grande Healthcare, L.P. v. Hawley, 284 S.W.3d 851 (Tex. 2009), the supreme court, in an issue that it labeled as "Failure to Give the Instruction," held that the trial court erred in not instructing the jury, as requested by the defendant-hospital, that it could not consider the acts or omissions of a defendant-doctor, who was not an agent of the hospital, when determining the hospital's negligence. 284 S.W.3d at 862-65. The trial court's liability question asked, "Was the negligence, if any, of the defendant-hospital, a proximate cause of injuries to the plaintiff?" Id. at 863. The court noted that the trial court had instructed the jury that the defendant-hospital "acts or fails to act only through its employees, agents, nurses, and servants" and certain evidence showed that the defendant-doctor worked in an office in the hospital and had "input" in the hospital's policy that its pathologists were to verbally notify doctors when a patient, like the plaintiff, was diagnosed with cancer. Id. The court explained that because the trial court had not defined the word "agent," the jury could have erroneously considered the defendant-doctor to be an agent of the defendant-hospital. Id. After concluding that the trial court had erred in denying the defendant-hospital's requested instruction, the supreme court, under the sub-heading of "Harm," concluded that the harm analysis of rule 61.1(b) "applies . . . because the jury could have found the defendant-hospital liable based on the defendant-doctor's acts or omissions under the charge as given, and there is no way for the defendant-hospital or an appellate court to tell if it did so." Id. at 865.