The doctrine of res judicata stands for the proposition that you cannot litigate the same matter twice. If you lose your case at trial, then with the exception of an appeal, that is the end of the matter.
In Innes v Bui, Ms. Bui had originally sued Ms. Innes in Provincial Court. The judge did not know who to believe so, as a result, dismissed the claim without formally making a liability determination. Ms. Innes then sued Ms. Bui in Supreme Court, however ICBC’S lawyer asked that the case be dismissed, claiming that the Provincial Court judge had already ruled on this matter with respect to liability. The Supreme Court dismissed the lawsuit, however the British Columbia Court of Appeal allowed the appeal. The Court of Appeal discussed the legal doctrine of res judicata.
 Where it applies, res judicata serves as an equitable estoppel. Its purpose is to ensure justice is done, prevent abuse of process, and fulfill the societal interest of finalizing litigation. The court retains a discretion to refuse to apply the principle where in special circumstances a rigid application would frustrate its purpose: Arnold v. National Westminster Bank Plc.,  2 A.C. 93 (H.L.) at 109-111.
 There are two forms of the doctrine of res judicata: cause of action estoppel and issue estoppel. Both operate where the court has adjudicated a cause of action between two or more parties and one of them seeks to re-litigate on the same facts. Where the cause of action is the same, cause of action estoppel operates to prevent re-litigation of any matter that was raised or should have been raised in the prior proceeding. Where the cause of action in the two proceedings is different, issue estoppel operates to prevent re-litigation of any issue determined in the prior proceeding.
 The pre-conditions to making out issue estoppel are stated in Angle v. Minister of National Revenue,  2 S.C.R. 248 at 254:
Lord Guest in Carl Zeiss Stiftung v. Rayner & Keeler Ltd. (No. 2), at p. 935, defined the requirements of issue estoppel as:
… (1) that the same question has been decided; (2) that the judicial decision which is said to create the estoppel was final; and, (3) that the parties to the judicial decision or their privies were the same persons as the parties to the proceedings in which the estoppel is raised or their privies …..
It seems to me that in the circumstances of this case, all that had to be considered on both motions before the court was whether the criteria set out in Angle had been met and, if they had been met, whether the court should exercise its discretion against applying the doctrine of res judicata.
 In my opinion, it cannot be said that the question of liability for the collision was adjudicated upon in the Small Claims proceeding. Having decided as a fact that the parties left their respective stop signs at “more or less the same time”, the Small Claims judge failed to consider the other important factual question before him – whether Ms. Bui had her left-turn signal on. Furthermore, he failed to consider the rules of the road imposed upon each of the parties under the applicable sections of the Motor Vehicle Act, R.S.C.B. 1996, c. 318 and how those rules would apply to the determination of responsibility in tort for the collision. This was not a case of inevitable accident or of no negligence. One or the other of the parties was wholly responsible, or liability was to be divided.
 The reasons of the Small Claims judge fell well short of deciding the negligence question. That issue remains alive in the Supreme Court action. The res judicata arguments of both parties fail.