36 Pa. Stat. § 3141.22
The said viewers having been duly sworn or affirmed faithfully and impartially to perform the duties required of them under the provisions of this act shall, at the time fixed for said first meeting or at any adjourned meeting, proceed to ascertain as accurately as may be the value of such bridge and to that end may require the attendance of any person whose testimony may be pertinent thereto and the production of any such books and papers as said viewers may deem necessary. If any person shall refuse to appear and testify before such viewers or refuse to produce such books and papers when thereto required, the said court or any judge thereof shall, upon application of said viewers or a quorum thereof, make such order therein as may be necessary.
36 P.S. § 3141.22