Can the outcome of a med-arb process be challenged as improperly combining the two roles?

Yes, this is a genuine and recognized concern with the med-arb model, precisely because the same professional moves from a confidential, facilitative mediation role into a binding, decision-making arbitration role over the same dispute. If a party can show that information learned confidentially during the mediation phase improperly influenced the arbitration decision, or that the switch between roles wasn't properly consented to or disclosed, this can potentially support a challenge to the resulting award on fairness or procedural grounds.

This risk is exactly why a well-drafted med-arb agreement addresses these issues upfront, spelling out what happens to information shared during mediation if the process moves to arbitration, and confirming both parties understand and accept that the same person will play both roles. Where the agreement handles this properly and the professional conducts the process carefully, med-arb can work well and hold up if later challenged. Where it doesn't, the combined process becomes a real vulnerability. Anyone considering med-arb should discuss these specific safeguards with a family lawyer before agreeing to the process.