The board, its members and the referees shall not be bound by the technical rules of evidence in conducting hearings and investigations, but all findings of fact shall be based only upon sufficient, competent evidence to justify them.

If any party or witness resides outside of the Commonwealth, or through illness or other cause is unable to testify before the board or a referee, his or her testimony or deposition may be taken, within or without this Commonwealth, in such manner and in such form as the board may, by special order or general rule, prescribe. The records, kept by a hospital of the medical or surgical treatment given to an employe in such hospital, shall be admissible as evidence of the medical and surgical matters stated therein, but shall not be conclusive proof of such matters.

Where any claim for compensation at issue before a referee involves five weeks or less of disability, either the employe or the employer may submit a certificate by any qualified physician as to the history, examination, treatment, diagnosis and cause of the condition, and the statements shall be admissible as evidence of medical and surgical matters therein stated, but such statements and certificates shall not be admissible in any subsequent proceedings.

Where an employer has furnished surgical and medical services or hospitalization in accordance with the provisions of subsection (f) of section 306,¹ or where the employe has himself procured them, the employer or employe shall, upon request, in any pending proceeding be furnished with or have made available a true and complete record of the medical and surgical services and hospital treatment, including X-rays, laboratory tests, and all other medical and surgical data in the possession or under the control of the party requested to furnish or make available such data.