Harvey, who covered the trial for KCBS, bought the Hollywood Hills house in 1984 from Wayne Hughes, who owned Public Storage. It was Wayne's bachelor pad, and he threw lots of parties. Among the guests ... his good friends O.J. and Nicole Brown Simpson.

During the trial, prosecutors wanted to call Wayne to the stand to testify about several occasions where Nicole came to the house in the middle of the night and cried out for help. She told Wayne O.J. had beaten her and she was scared of him. Judge Ito would not allow Wayne to testify.

That's not the end of the story. Not long after the 1994 murders, Wayne wanted to install telephone equipment in his home, and hired a guy named Jim Holcomb to do the installation. Jim was an LAPD officer who had been called to O.J'.s home over the years when there was a domestic disturbance. Jim installed phone systems as a side gig.

Well, Jim went to Wayne's house and encountered Al Cowlings, O.J.'s best friend who was driving the Bronco during the infamous low-speed chase. Al knows a lot ... a porn star he had dated told Time Magazine Al told her, the murder knife "sleeps with the fishes."

Harvey knows Al told Wayne shortly after the murders he needed help -- he had been arrested after the low-speed chase -- and he told Wayne if someone didn't give him help, he was going to spill the beans on what he knew about the murders.

Harvey believes Jim knows very well what Al told Wayne, and he presses Jim about it as part of TMZ's new documentary -- "TMZ Presents: O.J. How He Really Did It" -- and Jim's reaction is revealing, to say the least.