I know that O.J. was acquitted, and some believe he is innocent, but from my experience it is generally accepted as fact that O.J. was the killer. From O.J.'s psuedo confessions (both the 'If I Did It's book and his ramblings during the Branco chase) to a clear motive, means and opportunity, I believe that for the sake of this Ask, it is a safe assumption that O.J. committed the crime.
I apologize if this question doesn't fit the theme of 'history' but I couldn't find a more appropriate subreddit.
In the early stages of the trial, when Mark Fuhrman took to the witness stand, one of OJ's lawyers, Francis Lee Bailey, under oath, asked him if he ever said the word "nigger" over the past ten years, to which he said no.
Later in the trial, OJ's legal defense team found tapes of Fuhrman being interviewed about female police officers and police culture in general. In the recordings, as claimed by the defense team, Fuhrman said the word "nigger" 41 times and as recently as 1988, well within the past ten years. In the tapes, he claimed to have perpetrated violence against African-Americans and also describes how, as a police officer, he thought lying was sometimes necessary and claims that he has provided testimony regarding events that he did not witness.
This is a major problem for two reasons, first off, he was the one who found OJ's glove when he was the first responder to the scene and more importantly, it proved that he committed perjury, which is prosecutable, by lying under oath.
After much back and forth between the judge, defense and prosecution, the judge ruled that two excerpts from the tapes can be played to the jury: "We have no niggers where I grew up," and, "That's where niggers live.".
Now little context on Pleading the 5th (the right against self-incrimination), it's generally best practice to Plead the 5th on all questions instead of a specific one and not in all other questions. Once you invoke it your 5th Amendment rights, you cannot go back. A lawyer can almost definitely explain it more eloquently.
Since it proves that Fuhrman committed perjury, the defense asked him once more the previous question of "Have you ever said the word nigger within the ten years?". This is why he invoked his 5th Amendment rights; the defense team laid out a very clear trap where no matter, what the defense team would discredit both Fuhrman and more importantly the prosecution, in front of the jury since he was a key witness for the prosecution.
Once Fuhrman Plead the 5th in that question, the defense team asked damning questions such as whether he had ever falsified police reports or if he had planted or manufactured evidence to frame OJ for the murder, to which he Plead the 5th for all the following questions.
During the closing arguments of the trial Johnnie Cochran, the center of OJ's group of lawyers, referred to Fuhrman as "a lying, perjuring, genocidal racist" and compared him to Hitler. Also, he argued that Fuhrman had planted the bloody glove on O.J. Simpson's estate as part of a racially motivated plot against Simpson due to his racist beliefs.
One thing to keep in mind is that the jury was mostly comprised of African-Americans, one big reason for the defense stressing the racist language Fuhrman said. Also, the infamous Rodney King trial and aftermath was still fresh in people's minds, especially in the black community. The defense team was successfully able to play the "race card" for the jury and present the case that it is once again injustice by the LA court system against an African-American. But that's a whole other story.
This is one of the few cases where despite much evidence proving OJ committed the crime, the defense was able to spin the narrative that it is racial injustice and "the system" (aka the government, justice system, society, etc.) framed him because he was a (successful) black person. They spun this story so well that people even today, 14 years after the trial, still think he's not guilty despite all the evidence to the contrary.
If you get the chance, I highly, highly recommend the five-part documentary OJ: Made in America, which expands on all this and not only interviews the majority of the key players from the whole saga but breaks down the background and both micro/macro context to understanding the whole ordeal. It's a rare case of stranger than fiction and if the whole thing never happened and if it was a fictional story, few would find it hard to believe.
EDITs: Grammatical corrections, expanded some of the contexts and added the recommendation for OJ: Made in America documentary.