The report, commissioned by Democratic Attorney General Kathleen Kane and written by former federal prosecutor Geoff Moulton, blamed a three-year time lapse in filing charges on communication problems, an expungement of a 1998 complaint about the former Penn State coach and a failure to take certain investigative steps early on.
"The facts show an inexcusable lack of urgency in charging and stopping a serial sexual predator," said Kane, who had vowed to conduct a review of the investigation while running for office. "The report documents that more investigative work took place in just one month in 2011 than in all of either 2009 or 2010."
Moulton said his review, including internal emails by state prosecutors, "revealed no direct evidence that electoral politics influenced any important decision made in the Sandusky investigation."
Then-Attorney General Tom Corbett, a Republican, was in the midst of his successful 2010 gubernatorial campaign during the Sandusky investigation.
As a candidate in 2012, Kane said that Corbett may have had a political motive to slow down the investigation, an assertion Corbett has denied. The arrest of Sandusky led to the firing of longtime Penn State coach Joe Paterno while Corbett was serving as a university trustee; Penn State alumni and fans have objected to how Paterno was treated.
Corbett spokesman Jay Pagni said Monday that the investigation was conducted with the victims at the forefront.
"It was a thorough, thoughtful investigation, and in the end a child predator can no longer victimize anyone," Pagni said.
Sandusky was convicted in 2012 of sexually abusing 10 boys and is serving decades in prison sentence.
The report said the lead prosecutor at the time, Jonelle Eshbach, hectored her bosses about the case during a stretch in 2010 when the probe was largely dormant.
Eshbach drafted a grand jury report in March 2010 based on the claims of a lone victim, but she spent much of the ensuing months - as Corbett won the primary - trying to get approval for the report.
"In the interim, no witnesses were interviewed, no witnesses testified in the grand jury and no grand jury subpoenas were issued," Moulton wrote. He said the basis for that decision was that one accuser's testimony wouldn't be enough to convict Sandusky and an acquittal would make it harder to file more charges later.
According to the report, prosecutors told Moulton they waited until 2011 to search Sandusky's home computer and subpoena child protective services records because they "believed that they were unlikely to be productive and would have risked publicly revealing the existence of the investigation."
Two days after Corbett was elected governor in November 2010, the Centre County prosecutor received an anonymous tip directing investigators to assistant football coach Mike McQueary, whose testimony would eventually help convict Sandusky.
The investigation picked up steam after that, and authorities subpoenaed key figures at Penn State, including Paterno, vice president Gary Schultz and athletic director Tim Curley. Additional victims were identified, and on June 21, 2011, Sandusky's home was searched, producing photos and typewritten lists of children who participated in events at Sandusky's charity, The Second Mile, with some names highlighted.
More resources early on, including additional investigators, may not have speeded up the case, Moulton said, because the best leads in 2010 and early 2011 were not related to how many detectives were devoted to the matter.
He said decisions not to bring charges based solely on one accuser or, in June 2011, after three more witnesses had testified before a grand jury, "fit within acceptable bounds of prosecutorial discretion."
Moulton noted that if authorities had put together a broad-based team early on, it's possible someone may have known about or turned up a 1998 police investigation of Sandusky prompted by a mother's complaint that the coach had showered with her son. That report had been expunged, one reason for the lengthy investigation, he said.
Corbett said "electoral politics did not enter his thinking in any way," Moulton wrote, concluding the campaign donations Corbett received from people associated with The Second Mile does not appear to have affected the investigation.
The report does not go into depth about actions at Penn State, where three former administrators await trial on charges they participated in a criminal cover-up of complaints about Sandusky. The university eventually accepted a set of penalties from the NCAA over its handling of the matter, including a four-year bowl ban, a temporary reduction in football scholarships, the loss of 112 wins from Paterno's later years and a $60 million fine.