What happens if a defendant with a related claim does not bring it in the original case against the other defendant?

The correct answer is that the defendant can still bring the related claim in a separate action. This aligns with the principles of joinder and the way the Federal Rules of Civil Procedure function. If a defendant has a related claim against another party but chooses not to include it in the original case, they maintain the option to pursue that claim separately. This is particularly relevant in the context of related claims that are not compulsory counterclaims under Rule 13(a).

A claim is considered compulsory if it arises out of the same transaction or occurrence as the opposing party's claim, and failing to raise it in the original action could lead to a waiver of the right to bring it later. However, if the claim does not meet the threshold for being considered compulsory, the defendant has the flexibility to file it in a different case without losing their rights.

The other choices do not accurately reflect the procedural rules around joinder. The idea that a claim is automatically waived is only true for compulsory counterclaims, not those that are merely related. The assertion that the defendant loses the right to assert it in the future conflicts with the understanding that non-compulsory claims can indeed be pursued in subsequent actions. Finally, Rule 13(g) pertains to cross-claims, which