Frizzell started working in the Scottish Government in 1976, holding positions as director, locate in Scotland (1989-1991), chief executive Scottish prison service (1991-1999) and head of enterprise, transport and lifelong learning department (1999-2006).
- Independent member of audit committee, HM Prision Service, 2000-2008
- Adviser, Charteris plc, September 2006-September 2011. Approved by ACOBA, "subject to the condition that, for 12 months from his last day of service, he should not become personally involved in lobbying ministers or officials in Scotland on behalf of Charteris or their clients"
- Board member, Trefoil House, May 2006-April 2012
- Member of court, University of Abertay, Dundee, May 2006-December 2012
- Visiting Professor in public service management, Queen Margaret University, Edinburgh, 2006-
- Non-executive director and chair of audit committee, Scottish Ambulance Service, July 2011-
- Chair of court, University of Abertay, January 2013-