Judge Callahan, Cedar Falls, was appointed to the bench in 2000. He received his bachelor's degree from the University of Iowa in 1979 and his law degree from Lewis and Clark in 1984. Judge Callahan served in the U.S. Coast Guard from 1972 to 1976. After graduating from law school, he worked as a legal assistant/clerk for the City of Kenai, Alaska in municipal law from 1983-1984; as a district attorney for the Alaska Attorney General's office from 1985 to 1991 and in private practice from 1992-1996. He worked in the public defender's office from 1996 until his appointment to the bench. Judge Callahan is a member of the Iowa Judges Association, the Iowa State Bar Association, and the Black Hawk County and Alaska Bar Associations. He has two children. He was appointed as senior judge in 2018.