So it all starts with a black guy named Rodney King back in 1991. King was on parole for robbery and driving drunk one night and speeding. He lead police on a bit of a chase before eventually he was stopped. White LAPD officers ordered King and his passenger out of the car and to the ground.

Then things get messy - essentially King wasn't very cooperative with police and they thought he might be armed, so they used a "swarm" maneuver to take him down. King allegedly charged at one of the officers, they tazed him, and as he goes to the ground the officers proceed to take out their batons and beat King on the ground. King suffered numerous injuries - broken bones, skull fractures, brain damage, kidney damage. It just so happened that someone caught this on video.

Four of the white officers were indicted for excessive use of force. They were acquitted by a jury that contained no black people. Media reaction at the time was sort of stunned at the result. The video seemed very clear that it was excessive. Then-President Bush made national remarks that he was surprised by the verdict. (of note - later the 4 officers were also federally indicted and two were convicted and spent 30 months in prison due to the incident)

Hours after the verdict, riots started in Los Angeles that lasted for 6 days (1992). The black community felt the Rodney King incident was an example of long standing mistreatment by the LAPD and a justice system that failed to protect them and hold white police officers accountable.

So, now OJ in 1994. You have a black man accused of killing a white woman. Who was investigated by an agency that was known for having a bias against black people. The defense capitalized on this with one of the detectives - Mark Fuhrman. Fuhrman denied being a racist and using the N-word regularly, testifying that maybe he did once years prior. Unfortunately, Fuhrman had given an interview to an screenwriter years earlier where he extensively used the N-word (40+ times) and talked about how black people were treated by officers. Fuhrman was convicted of perjury as a result. The defense for OJ then painted Fuhrman as a racist, an agent of a racist agency (the LAPD), and if you can't trust them then you can't trust any of the prosecution's evidence.

Polls at the time, even before the verdict, showed a majority of white people thought he did it and a majority of black people thought he didn't. Many people still called back to Rodney King which was only a few years earlier to say the system and the police were biased. Living through the time you'd hear white people remark about "how black people could let a murderer go" and you'd hear black people remark about "how could white people ignore what the police were doing."

Obviously there's a ton of stuff written and done on it. Almost everyone involved in the trial wrote their own book - including the jurors. I highly recommend Marcia Clarke's book and even better Chris Darden's. Darden has an interesting perspective on the black community and his role as a black prosecutor on the case (the jurors' book felt Darden was a "token black" used by the prosecution). And the recent documentary Made in America is very well done as well. If you prefer a more dramatic interpretation, the People vs. OJ Simpson miniseries did a fairly decent job at capturing the racial element of the story.