Holbrook’s April 1 election will decide whether the position of police chief should be removed from civil service — a change that would give the town more flexibility in hiring, but also make the job more subject to political influence. The Board of Selectmen voted unanimously Feb. 21 to place the matter on the spring ballot. The move follows a contract impasse between the board and William Marble, who was chief until last month. As a result, Marble stepped down to sergeant, the highest rank below chief in the 20-member department. Three patrol officers applied to be chief as part of the civil service system; none of the sergeants applied. Marble said sergeants can earn more than the chief because they have more opportunity to do overtime and details.