Chris Koster

Chris Koster was born on August 31, 1964.  He is an American lawyer and politician who served as the 41st Attorney General of Missouri from 2009 to 2017.  Before he was elected attorney general, he had served in the Missouri Senate since 2005, representing the 31st Senatorial District as a Republican until August 1, 2007, when he switched to the Democratic Party.  He was the Democratic nominee for Governor of Missouri in the 2016 election and was defeated by Republican nominee Eric Greitens in the general election.

Koster was born and raised in St. Louis, where he attended Saint Louis University High School and graduated from the University of Missouri in Columbia.  He received his Bachelor of Arts degree in 1987.  In 1991, he received his Juris Doctor degree from the University of Missouri School of Law.  He also earned his master of business administration from Washington University in St. Louis in 2002. Before becoming a county prosecuting attorney, Koster practiced law with the Kansas City law firm of Blackwell Sanders from 1993 to 1994.  He also served as an Assistant Attorney General from 1991-93.

Before his election to the Missouri Senate in 2004, Koster served as Prosecuting Attorney of Cass County.  He was first elected prosecutor in 1994 and was reelected in 1998 and 2002 by a wide margin.  As a prosecutor, he enforced Missouri’s criminal laws in Cass County. In addition, his office served as the civil counsel for all non-criminal matters before the county government.  He led investigations into many of Missouri’s most notorious criminal cases, including the investigation against serial killer John E. Robinson. He has developed extensive trial experience from his supervision of over 20,000 cases.

Political Highlights of Chris Koster

Koster made Missouri political history when he announced that he left the Missouri Republican Party to become a Democrat.  Citing his longstanding differences with the Republican Party on stem cell research, workers’ rights, and the non-partisan court plan, Koster said that the Missouri Republican Party had become too beholden to the extreme right-wing to lead the state of Missouri.  He said, “Today, Republican moderates are all but extinct.”

Before he changed parties, Koster was chairman of the Republican Caucus, the majority party’s fourth-ranking position in the Missouri State Senate.


Koster’s career is not without controversy.  He barely defeated State Representative Margaret Donnelly in the Democratic primary for the nomination for Missouri Attorney General.  Koster won despite accusations that his campaign violated state law in raising money from multiple committees.   He also survived the disclosure that he played a supporting role in a plagiarism episode that damaged Attorney General William L. Webster’s campaign for governor in 1992.  His campaign victories were not easily won because he had to overcome the label of “opportunist” due to switching parties during the ’08 election.  He then defeated Republican State Senator Mike Gibbons in the general election, 52.83% to 47.17%.  He was sworn in as attorney general on January 12, 2009, succeeding Governor Jay Nixon.