In Panos v. Great Western Packing Co. (1943) 21 Cal.2d 636, P sued D1 and D2 for personal injuries on the theory D1 permitted D2 to act negligently, to plaintiff's harm. A judgment was entered for defendants and, no appeal having been taken, became final. Four months later, P sued D1 (only) again, this time on the theory that D1 was directly negligent in causing plaintiff's injuries. Defendant pleaded the prior judgment as a bar to plaintiff's second suit. The trial court dismissed the action and, on appeal, a unanimous Supreme Court affirmed. Chief Justice Gibson's opinion underlines an important feature of the res judicata doctrine, namely, it is not the fact of actual litigation of a claim that raises the bar to its subsequent relitigation, but the opportunity to litigate claims. So long as a plaintiff has the opportunity in litigation to present claims for relief resting on and derived from the same primary right and fails to do so, a subsequent suit raising those claims is barred by res judicata principles. "The doctrine of res judicata rests upon the ground that a party to be affected, or some other with whom he is in privity, has litigated, or had an opportunity to litigate the same matter in a former action in a court of competent jurisdiction, and should not be permitted to litigate it again to the harassment and vexation of his opponent. Public policy and the interest of litigants alike require that there be an end to litigation." ( Panos, supra, 21 Cal.2d at p. 637, ) Quoting 2 Freeman on Judgments, section 676, page 1425, the Panos court wrote that "the first judgment is deemed to adjudicate, for purposes of the second action, not only every matter which was, but also every matter which might have been urged in support of the claim in litigation." ( Panos, supra, at p. 638, )