There's a school of thought out there that Joe Paterno might have committed perjury in front of the grand jury because of knowledge of the 1998 incident. I had a recent experience that illustrates why I think this argument doesn't work.
The story: On June 30 I started a 16-day road trip out West, and on the first night, south of Chicago on I-80 I get pulled over around 2:00am for doing 72 in a 55, which was true because it was a construction zone (not much of one, they just reduced three lanes to two) and I somehow missed the drop in speed limit. In summary, I get a warning for going 64, then the officer asked to search my car because they "had a job to do." I consented, having nothing to hide and being kind of tired at that point. So for a good 20-30 minutes he searches the car, and my belongings for drugs and contraband, and finally finishes and sends me on my way with just the warning.
This is a true statement: I was investigated for running drugs and contraband in my Camaro at 2am near Chicago. It is also a fact that I was truly not guilty of the thing I was being investigated for. (Though I may have "boundary issues" with speed limits . . .). So, in general, when someone is investigated but not charged, it is reasonable to conclude that they are not guilty of the thing they are being investigated for. I think I always knew this theoretically, but having this experience really drove home the point for me.
So here's how this relates to the idea of perjury as it pertains to Joe. The grand jury asked him:
Q: Other than the incident that Mike McQueary reported to you, do you know in any way, through rumor, direct knowledge or any other fashion, of any other inappropriate sexual conduct by Jerry Sandusky with young boys?
It seems to me that the most Joe could have known about 1998 is that Sandusky was investigated, but not charged. Given that, and given that is perfectly legitimate to think that being investigated but not charged means that the subject of the investigation is not at all guilty of what it was they were being investigated for, it is fully truthful to answer:
Mr. Paterno: I do not know of anything else that Jerry would be involved in of that nature, no. I do not know of it.
He was asked if knew of 'inappropriate sexual conduct'. It was fully truthful of him to answer "no", because being aware of an investigation where the subject isn't charged does not constitute knowledge of such conduct.