Under Rule 13(a) of the Federal Rules of Civil Procedure (FRCP), entitled “Compulsory Counterclaim,” the defendant must plead a counterclaim that arises out of the same “transaction or occurrence” as plaintiff’s main claim, or it is deemed waived. See Siegel, New York Practice §632 (Thomson 5th ed. 2011). The risk of waiver based on a pleading failure suggests that any doubt about whether a counterclaim has the kind of relationship to the main claim that would make it compulsory should be resolved in favor of pleading it instead of suing on it separately. This is especially so because the policy underlying this rule is judicial economy. See Transamerica Occidental Life Ins. v. Aviation Office of Am., 292 F.3d 384, 389 (3d Cir. 2002).
The “transaction or occurrence” standard in FRCP 13(a)(1)(A) has been liberally construed by most courts and looks to whether claims “‘are so logically connected that considerations of judicial economy and fairness dictate that all the issues be resolved in one lawsuit.’” United States v. Aquavella, 615 F.2d 12, 22 (2d Cir. 1979). In other words, for a claim to qualify as a compulsory counterclaim under FRCP 13(a), there need not be a precise identity of issues and facts between the main claim and the counterclaim. See Xerox v. SCM, 576 F.2d 1057, 1059 (3d Cir. 1978).
