WorldNetDaily had a good series in the end of 1998 about one Bill Wasz, who OJ's lawyer Kardashian had hired to stalk Nicole and take notes on her moves, and steal her car. It seemed Kardashian was setting up this Wasz as a patsy for an eventual hit on Nicole. It blew up when Wasz didn't keep up his end of the bargain and got arrested after a car chase.
This would support the scenario that OJ/Kardashian wanted Nicole killed. However, I believe OJ himself was the knifeman after these carefully-laid plans fell apart, though I wouldn't totally discount the possibility that he had someone else do it -- the forensic evidence points to OJ, even with the LAPD's questionable practices.
It seems netither the prosecution nor the defense wanted to call Wasz to the stand because he had information on drug use/dealing/etc. by OJ's crowd and other powerful people in LA -- and neither side wanted to go there. This unwillingness to lay out all the evidence ultimately damaged the prosecution case against OJ.
See this link and/or punch in "Wasz" on WND's search engine for the whole 11-part series.