He probably helped OJ by pleading the 5th, he should have just answered the questions honestly misleading or not. If I was on a jury and a lead investigator was asked on the stand if he planted evidence and the cop pled the fifth more than likely I am voting to acquit all of the evidence is potentially tainted. Also it sounds like he abused his 5th amendment right, the right is there to protect you from criminally incriminating yourself if his only motivation was to not let the defense mislead the jury he was being an asshole and could have potentially been compelled to testify.