Johnnie Cochran, Jr. began his legal career in Los Angeles as a Deputy Attorney for the city's criminal division. Cochran worked his way through the ranks to accept a position as Assistant District Attorney for Los Angeles County. While the Assistant D.A. for Los Angeles County, one of Cochran's subordinates was Lance Ito. Cochran left the D.A.'s office to start his own firm, handling both criminal and civil cases.

The day of the low-speed Bronco chase to the Rockingham mansion, Cochran was scheduled by the television show Nightline as a legal expert to comment on the developments of the day. While on camera, Cochran declared Simpson to be "presumed innocent." However, off camera, Cochran told a friend, "O.J. is in massive denial, he obviously did it."

Shapiro hired Cochran at Simpson's request. Cochran had known Simpson casually prior to representing him, though only casually. Cochran's willingness to meet with Simpson in jail helped Cochran to find favor with Simpson, and ultimately to displace Shapiro as lead counsel.

Cochran almost took the approach of a "black preacher" to the mostly African-American jury, quoting scripture and raising his voice in heightened fervor. During the trial, legal observers gave excellent reviews of Cochran's courtroom style and ability. However, Cochran has been criticized for his use of the "race card" in his defense of Simpson. Even his co-counsel, Robert Shapiro, was to accuse him after the trial of dealing the race card "from the bottom of the deck".

In addition to O.J. Simpson, Cochran's high profile clients have included Michael Jackson, Reginald Denny, Abner Louima, Geronimo Pratt (former Black Panther), Todd Bridges, James Brown, Angela Igwe, and Cynthia Wiggins. Cochran has been selected as one of the best trial lawyers in the country in 1994. Cochran has written his autobiography, Journey to Justice, and drives a Rolls-Royce with the vanity plate "JC JR."