When irregularities in an officer's election or appointment are subsequently discovered, (i.e., an officer fails to file an official oath or the officer's term has expired and the officer is not entitled to hold over until a successor is appointed and qualifies), the officer is usually considered a "de facto officer." In Wisconsin, the "acts of a de facto officer are valid as to the public and third parties and cannot be attacked collaterally." Walberg v. State, 73 Wis.2d 448, 464-64, 243 N.W.2d 102, 105 (1976). The de facto officer's acts are binding and valid until the individual is ousted from the office by the judgment of a court in a direct proceeding to try the officer's title to the office. Id.