Most institutional arbitrations require witnesses to file a written witness statement in advance, setting out their evidence in full — this generally substitutes for oral examination-in-chief, which is one of the more significant time savings arbitration offers over conventional court trial.
At the hearing itself, witness testimony is typically confined to cross-examination by the opposing side and limited re-examination or clarificatory questions from the tribunal, rather than a full oral account being given from scratch.
Expert witnesses follow a similar pattern — a written expert report exchanged in advance, sometimes followed by a joint expert conference (where opposing experts meet to narrow points of agreement and disagreement before the hearing), with oral testimony at the hearing focused on the points still genuinely in dispute.