When Does May Mean Must?
In any reasonable civil procedure world, there ought to be a close relationship between the parties' right to join claims in their first lawsuit and the scope of res judicata in subsequent suits between them. If, for example, the rules of joinder did not allow plaintiffs to join counts for property damage and personal injury in a single lawsuit, it would be a rigid system indeed that barred an accident plaintiff who had sued for damage to his car in one suit from bringing a separate action to recover for his personal injuries in the accident. Similarly, if the joinder rules limited a plaintiff to proceeding on a single theory, such as negligence, in his first suit, it would be unfair to bar him from starting a second action on a strict liability theory. One way or another, the system ought to offer parties a chance to have all of their claims heard, either through limited claims in multiple suits or multiple claims in a single suit.