Corbett said on ABC's "This Week with Christiane Amanpour" criminal investigations in general often result in witnesses and suspects brining new information to light.
"The one thing you learn when you're conducting investigations is that, as people face charges, they may start to cooperate, they may start talking about different things," Corbett said.
He said the Penn State scandal, for example, grew out of a different investigation.
"The attorney general became involved, not in a case related to the university, but in a case from a next-door county, Clinton County, and a school there, where Mr. Sandusky was helping out as a coach," he said.
Corbett said a major focus of the state investigation will be to determine how far up the chain of command at Penn State reports about Sandusky went and why witnesses told their bosses instead of calling police directly.
"I'm sure that the facts will be determined as to exactly how far up that knowledge was passed through the chain of command," he said.