Though the cases have yielded conviction after conviction, they have been fraught with controversy, none more so than Sandusky's. How that probe was run by then-Attorney General Tom Corbett, and whether it took too long, is a matter under review by the new attorney general, Kathleen Kane.
In that matter, the investigator fully expects to be investigated.
"I welcome being questioned," Noonan said during a recent interview in his office at state police headquarters outside Harrisburg. "I'm not upset, I don't feel any fear, I'm ready to cooperate . . .. People can have a difference of opinion about how long it took and whether it should have been done differently. But I've been doing this for over 40 years, and I think we did this exactly the right way."
That stance is, those who know him say, quintessential Noonan: not easily agitated. Takes few things personally. Figured out early on that a sense of humor is essential to getting through life.
He says he learned that lesson in Vietnam.
He was a forward artillery observer, directing artillery and mortar fire and communicating battlefield intelligence.
You can ask him about the war, but, like many veterans, Noonan prefers not to speak of it. He will say he saw "a lot of death" and will acknowledge that the 22-year-old who went to Vietnam came back forever changed. He'll deflect questions about the Bronze Star citation hanging on his office wall.
The citation tells of "courage and composure under fire" on the day his unit came under attack and Noonan, "seemingly oblivious" to the rain of enemy fire, rushed to evacuate the wounded.
"That's Frank - that kind of loyalty to his men and commitment to duty carries over into everything he does," said Randy Feathers, who led a team of attorney general's agents and state police on the Sandusky case, working closely with Noonan.
"I loved working with him, we all did - he had confidence in you and let you do your job," said Feathers, now a state parole board member.
Growing up in Morrisville in lower Bucks County, Noonan decided early on against a soldier's life, knowing how hard that life could be on a family. His father was a prisoner of war for three years in World War II, returning a frail 93 pounds.
So after Vietnam, Noonan began a 27-year career as an FBI agent - in Wisconsin, Iowa, and finally central Pennsylvania, investigating everything from bank heists to kidnappings to drug gangs. When he retired in 1998, he became regional head of the state attorney general's narcotics unit in Wilkes-Barre, under then-Attorney General Mike Fisher and later, under Corbett.
Noonan loved his time there. Overseeing major drug cases, he developed a knack for catchy code names: Operation Bone Crusher (a $2 million cocaine ring), Operation Smackdown (a big-bucks heroin ring), Operation Bad Rap (a cocaine-and-marijuana ring).
He also showed a knack for getting hardened criminals to confess, remembers Francis P. Sempa, a federal prosecutor who worked with Noonan in the 1980s and '90s.
"It was really an amazing thing to observe," said Sempa, a state prosecutor in Wilkes-Barre at the time. "I can't explain it, but I think they would confide in him because Frank treated them with respect and was probably the first person in a long time who treated them with respect."
Admirers say it's no act.
"He is completely genuine," said Christopher Abruzzo, who headed the attorney general's drug strike force section and is now Corbett's acting environmental secretary. "I don't think there is a phony bone in his body."
As attorney general, Corbett took a shine to Noonan, said longtime Corbett spokesman Kevin Harley, who knows both men well. Both were Irish; both were in law enforcement and had worked for the feds - Corbett as U.S. attorney for Western Pennsylvania. "He used to call Frank 'my FBI agent,' " Harley said.
It was Corbett who, as attorney general, persuaded Noonan to come to Harrisburg to run the office's criminal investigations in 2009. He landed in a beehive of activity - and pressure. Bonusgate was under way, and the Sandusky probe had begun.
Noonan describes the Bonusgate prosecutions as the most draining, if only because of the volume of e-mails and documents involved in building the cases against legislators and their aides for illegally using state staff and money for political work.
As for Sandusky, Noonan agreed with Corbett on a crucial point: He did not think the first young accuser's account was enough to build a case against the former football coach, a popular, charismatic figure.
"I personally never felt comfortable with that," Noonan said. "I always thought, if we can get more evidence, we needed more evidence. And I know the prosecutors did."
What Kane's investigators may hear if they question Noonan is a brisk defense of how the case was handled. Noonan says he saw no hint of foot-dragging or politicking - suggestions that have swirled despite Corbett's denials. Noonan says his longtime friend did it by the book.
"No matter what information was brought to him, no matter who it was about, he was very much 'do what's right,' " Noonan said. "And that's what we did."
When Corbett became governor in 2011, he asked Noonan to run the state police, overseeing a $195 million department whose troopers go after everything from speeders and liquor-law violators to crooked politicians.
The move was risky. Noonan was the first person in decades from outside the ranks to be named to the $142,300-a-year post.
"At first I thought, 'Boy, this could be a disaster,' " Abruzzo said. "But he has done a marvelous job there. And from the men and women that I've known who have been there for years, they were even astonished by how well he assimilated into that agency and made people feel good about the organization."
Noonan chose not to wear a state police uniform - a gesture troopers took as a token of respect for their work.
"That said a lot," said Joseph Kovel, who heads the troopers' union. "We've had a very good working relationship with him."
As for his next move?
"I don't worry about tomorrow and whether this will happen or that will happen," Noonan said. "I remind myself almost every day: What you are doing right now, do it well."
Contact Angela Couloumbis at 717-787-5934, firstname.lastname@example.org, or follow on Twitter @AngelasInk.