Prior to this, he served as a Democratic member of the Illinois Senate and an associate judge in the Will County court system.

In 1966, he joined the United States Marine Corps where he flew over 200 missions as a helicopter machine gunner during the Vietnam War.

[2] During his legal career he worked in the office of the Cook County Public Defender and as a partner in the Joliet law firm of Dunn, Martin and Miller.

[2] In the 1991 Republican controlled decennial redistricting process, Dunn was drawn into the 43rd district with fellow Democratic incumbent Jerome J. Joyce.

Governor Jim Edgar charged the task force with the responsibilities to study future space needs, including costs, for correctional facilities; consider cost-effective alternatives to imprisonment; analyze current policies, statutes and sentencing procedures that affect inmate population; and identify solutions that protect both taxpayers' safety and their pocketbooks.