As District 5 Supervisor Ross Mirkarimi threw his hat into the ring for the seat held for 31 years by San Francisco Sheriff Mike Hennessey, the predecessor of Mirkarimi’s district representing Japantown was surprisingly named the chief assistant to Public Defender Jeff Adachi.

Former San Francisco supervisor, mayoral candidate, and U.S. vice presidential candidate Matt Gonzalez returned to public service Feb. 22 as chief attorney for the public defender’s office.

Gonzalez worked as a deputy public defender from 1991 to 2001, when he took office as supervisor, and will replace former Chief Attorney Teresa Caffese, who resigned on Jan. 31.

The post is essentially second-in-command to the public defender.

“We wanted a top trial lawyer who understands our work, has a commitment to our clients and a dedication to preserving the resources that allow our office to function,” Adachi said in a statement.

Mirkarimi, meanwhile, filed papers to run for sheriff on Feb. 22, just four days after Hennessey announced he would not be seeking re-election this November.

Prior to Mirkarimi’s election as supervisor in 2004, he worked for nearly nine years in the San Francisco District Attorney’s Office as an investigator specializing in economic and environmental crimes.

He is the chair of the board’s public safety committee and is also a graduate of the San Francisco Police Academy, where he was class president.

If Mirkarimi is elected in November, the mayor would appoint his replacement as supervisor for the rest of his term, which ends in January 2013.