In a medical malpractice case, is a doctor required to provide expert testimony on the issue of contributory negligence?

In Barton v. Owen (1977) 71 Cal.App.3d 484, 506, the appellate court wrote: "[W]here contributory negligence arises in a medical malpractice context there is need for the defendant to have offered expert testimony on the issue. Only experts can testify regarding the proximate effect of the plaintiff's actions upon the aggravation of his condition. In much the same way that laymen are not qualified to judge whether a doctor has been negligent because of their lack of common knowledge on the subject, they also are not qualified from a medical standpoint to determine the effects of the 'negligent' acts of the plaintiff. We note in passing that this might not always be the case. For when a doctor's negligence is 'obvious' to anyone as a matter of common sense, i.e., the leaving in of a sponge, so might there arise similar situations on the part of the plaintiff where his negligence is similarly 'obvious.'"