53 Pa. Stat. § 30475
The members of such court of inquiry or trial shall be selected as follows, namely: The director of the department of public safety shall, in the presence of the accused and a brother officer acting as his counsel, as aforesaid, cause the names of at least twenty-five members in said police or fire department, equal or superior in rank to the accused, to be written upon separate slips of paper of the same size, color and texture, and folded or rolled so that the names thereon cannot be distinguished until drawn as hereinafter provided, cause said slips to be placed in a box from which the same are to be drawn by lot by some disinterested person until seven names have been drawn therefrom; whereupon the director of the department of public safety and the accused shall each in order be entitled to exercise challenges until only three names are left, and said three persons shall compose said court, either of trial or inquiry, as the case may be.
53 P.S. § 30475