 From 1981 to 1982, Viken was a partner in the Rapid City, South Dakota law firm of Finch, Viken & Viken, and then from 1981 to 1992, Viken was a partner in the Rapid City firm of Finch, Viken, Viken & Pechota.From 1992 until 2003, Viken served as a partner in the Rapid City law firm of Viken, Viken, Pechota, Leach & Dewell, LLP.In 2003, Viken was appointed federal public defender for the District of South Dakota by the United States Court of Appeals for the Eighth Circuit.