Federal Rule of Evidence 408 is kind of a funny thing. It says that settlement conduct and discussions are inadmissible "to prove or disprove the validity or amount of a disputed claim" or for impeachment.
That's significant, but it leaves open a lot of potential uses of settlement communications throughout the case—not to mention in later cases, potentially on different claims. The rule explicitly sets forth that such communications and conduct are still admissible for other purposes:
(b) Exceptions. The court may admit this evidence for another purpose, such as proving a witness’s bias or prejudice, negating a contention of undue delay, or proving an effort to obstruct a …
