Reiner earned a Bachelor of Science degree from the University of Southern California and a Juris Doctor from the Southwestern Law School in 1964.

[1][2] From February 6 to July 17, 1970, Ira Reiner represented Leslie Van Houten in the Tate-LaBianca murder trials.

[4] As district attorney, he supervised the prosecution of several notorious cases, including the murder trial of Richard Ramírez, the widely publicized police arrest of Rodney King, and the McMartin preschool trial, the best known case of day care sex abuse hysteria.

In 1990, Reiner was an unsuccessful candidate for the Democratic nomination for California attorney general, losing to San Francisco District Attorney Arlo Smith, who in turn was defeated by Republican former Congressman Dan Lungren.

In 1992, Reiner sought re-election as district attorney, but trailed Gil Garcetti in the June non-partisan primary.