Secretary Kernan served as CDCR Undersecretary for Operations from March to December 2015. He was owner at Kernan Consulting from 2011 to 2015. He served as Undersecretary for Operations at CDCR from 2008 to 2011. He was Chief Deputy Secretary of Adult Operations from 2007 to 2008 and Deputy Director of Adult Institutions from 2006 to 2007.
He served as Warden at California State Prison, Sacramento, from 2004 to 2006 and Warden at Mule Creek State Prison from 2003 to 2004, where he also served as a Chief Deputy Warden from 2001 to 2003 and as a Correctional Administrator from 2000 to 2001.
He served as a Correctional Captain from 1991 to 2000, as a Correctional Lieutenant from 1987 to 1991, an Associate Budget Analyst from 1986 to 1987, a Correctional Sergeant from 1985 to 1986 and a Correctional Officer from 1983 to 1985. He served in the U.S. Navy from 1979 to 1982.