Impartiality is one of the more commonly recognised aspects of the role of the Mediator. This does not mean that the Mediator should somehow become inhuman and not have a feeling of bias towards one party or another, but that they practice in a way that minimises any manifestation of this bias. This is an important distinction to make. No-one can genuinely claim to be impartial, but they can continually review their own feelings and thoughts about someone or a situation in order to acknowledge this and then monitor, and adjust where necessary, their practice as a mediator in the light of this awareness.
His words are just as applicable to Ombuds. (Mediate.com.)