O'Toole is a small business owner and a member of the politically influential Plumbers and Pipefitters Local 562 labor union.
A 1976 graduate of Cleveland High School in St. Louis, O'Toole attended Western Illinois University and graduated from the University of Missouri–St. Louis with a bachelor of science degree in business and marketing.
He served as a lieutenant in the sheriff's department for twelve years in the City of St. Louis, as a supervisor in the service department.
Awards received by O'Toole include Awards of Appreciation from the Missouri Pest Control Association, the Missouri Police Chiefs Association and the Judiciary Award of Appreciation.
As a result of redistricting in 2002, District 68 moved to Barry and Stone counties in southwestern Missouri. After leaving the legislature, O'Toole served for a time as Democratic director of the Board of Election Commissioners for the City of St. Louis. He also made an unsuccessful bid for the Democratic nomination for Ward 16 alderman in St. Louis in 2003.
O'Toole resides in the Princeton Heights neighborhood of St. Louis with his wife, Ronda, and children, Alexandra, Timothy and Katherine.