A concerned citizen can try to sue to void the settlement. Depending on the jurisdiction, courts adopt one of two rules for consideration regarding a sketchy legal claim for settlement agreements that get challenged later.  1) As long as the legal claim (wrongful death in this case) was foregone in a "good faith" belief that they could recover, there is consideration and the settlement is fine. 2) The one we want, if the legal claim that was given up as consideration for the settlement was completely invalid, then the settlement is voided.