Thicker Still

P, a passenger in O's car, was injured when the car collided with a taxi driven by D. P sues D. D seeks to introduce evidence of settlements between D and O, where O agreed to pay for damages to D's vehicle, and between P and O, wherein O paid P an undisclosed amount for P's injuries. What ruling and why?

Even when evidence of a completed settlement is not offered against a party, can it be excluded under Rule 408 if offered to prove "invalidity of the claim or its amount"?

In this case, in contrast to Problem III-10, D seeks to introduce evidence of a settlement between himself and the driver (O) of the car in which P was riding, wherein O agreed to pay for damage done to D's vehicle. The inference that D would like the jury to draw from this evidence is that O's payment to D for property damage constitutes an implied admission that O was at fault in the accident. D also seeks to introduce evidence of P's earlier settlement with O, the driver of the vehicle in which P was riding. The inferenceD would like the jury to draw from this evidence is twofold--that O admitted his fault by paying P and that P has already been compensated, at least in part, for his injuries. In many states, joint tortfeasor law may require settlements with co-defendants to be revealed to the jury upon the trial of nonsettling defendants. How would such a provision of state law be reconciled with Rule 408 in a diversity case in federal court?