The board of supervisors shall not allow to the collector a credit for the insolvent list he reports, merely because he presents it duly sworn to, but the board shall examine carefully each election district and city, town, or village list as reported, and shall scrutinize each name and amount reported insolvent, and shall use any knowledge had by any member of the board, and avail of any information by witnesses to test the accuracy of the report. The board shall not allow the collector credit for the taxes of any delinquent who may be ascertained to have anything in possession or in action by a sale of which the collector would be able to make the taxes; and all of the list for which the board shall not allow a credit shall be charged against the collector.