Code of Federal Regulations Title 29. Labor § 29.18.103 Rulings on evidence

(1) Objection. In case the ruling is one admitting evidence, a timely objection or motion to strike appears of record, stating the specific ground of objection, if the specific ground was not apparent from the context;  or

(2) Offer of proof. In case the ruling is one excluding evidence, the substance of the evidence was made known to the judge by offer or was apparent from the context within which questions were asked. A substantial right of the party is affected unless it is more probably true than not true that the error did not materially contribute to the decision or order of the judge. Properly objected to evidence admitted in error does not affect a substantial right if explicitly not relied upon by the judge in support of the decision or order.