California Code, Labor Code - LAB § 5708

All hearings and investigations before the appeals board or a workers' compensation judge are governed by this division and by the rules of practice and procedures adopted by the appeals board. In the conduct thereof they shall not be bound by the common law or statutory rules of evidence and procedure, but may make inquiry in the manner, through oral testimony and records, which is best calculated to ascertain the substantial rights of the parties and carry out justly the spirit and provisions of this division. All oral testimony, objections, and rulings shall be taken down in shorthand by a competent phonographic reporter.