That's a good question, one I've thought about quite a bit. In my opinion, 98 could be the starting point because that was the year Sandusky learned he would not become the next head coach at PSU. Perhaps the disappointment caused him to snap and fall deeper into his compulsion. Or maybe he just didn't care anymore and was willing to throw caution to the wind once the prospect of becoming the next head coach was no longer there. Also, there is the possibility his blatant crimes within the football building were a passive-aggressive attempt to damage Paterno. If so, then he certainly succeeded.
But there is also the possibility that he was not to become the next head coach because of a previous incident that was concealed. Here is a note, included in the Freeh report, that Paterno wrote, presumably, around 98:
Does it sound like Paterno knew about an allegation? Does it sound like Paterno finds Sandusky's obsession with the charity a bit creepy?
I tend to think not. I believe Paterno bought into the mythology he created about the Penn State football program, and he really believed one of his assistant coaches would rather spend time doing charity work than coaching football.
Of course, that only relates to Paterno. There are plenty of other folks in Centre County associated with Second Mile, law enforcement, CYS, etc. that could have had knowledge of his criminal behavior.
