matter of record

Definition from Nolo’s Plain-English Law Dictionary

Anything in the record of the court. This may include testimony, evidence, rulings, and sometimes arguments which have been recorded by the court reporter or court clerk. It is an expression often heard in trials and legal arguments to refer to a fact recorded by the court in the course of a hearing. For example, if it was determined in cross-examination that Ms. Smith goes by another name, a lawyer might say "Ms. Smith's alias is a matter of record."

Definition provided by Nolo’s Plain-English Law Dictionary.