The grand jury report states that Joe was told what McQueary had seen. McQueary states he saw Sandusky raping a ten year old. Joe knew.
In 2002. After Sandusky was retired. Even then the AD and the VP still said there was nothing there. He had the word of one man v. the entire PSU apparatus.
Now, should Joe have made the effort to put 2+2 together and realize there was something there and followed up? Yes he should have. He didn’t because or moral cowardice, self-absorbedness, CYA, and negligent inaction and just didn’t want to see. That doesn’t mean he KNEW and you certainly can’t prove with the info we have that he KNEW in 1998.
And it certainly doesn’t mean he protected Sandusky. We have no evidence he used his position to do so.