The motion, which allows for new charges to be filed, came after Ferman acknowledged that her office had botched the case by misreading a urine analysis. Ferman asked the state to take over the case, saying she had a conflict of interest because she was conducting an internal review of her office's conduct.
So now, state Attorney General Kathleen Kane's office will review the evidence that prosecutors assembled. It also is likely to question the alleged victim and other witnesses on its own.
"You have a very, very serious charge here, and you have an individual who has come in as a victim and evidently given full cooperation to the police," said Bruce A. Antkowiak, professor of law and director of criminology at St. Vincent College in Latrobe, Pa.
"Much of the assessment Kane's office will make is the same it would make in any case," he said, including assessing the strength of victim testimony and other evidence. "The charges do not appear to have been dropped because prosecutors suddenly believed they did not have a prosecutable case."
Kane might be able to proceed with trying Kerns on the most serious charges, said Stephanos Bibas, a University of Pennsylvania professor of law and criminology and former federal prosecutor, even without the presence of the sleep aid Ambien, which earlier was thought to have been a factor in the case.
Bibas said that because the accuser drank at the office party, and consumed more alcohol in Kerns' car, even the charge of raping an unconscious person could still apply.
"It can be much, much harder when it's alcohol," he said, than when there is evidence that the accused slipped a drug to the alleged victim.
As the county attorneys did, he added, state prosecutors might file a number of charges against Kerns to give them flexibility in offering a plea bargain and getting a conviction on some counts.
The key consideration, advocates for rape victims said, is whether the accuser was able to consent to the sex.
"If somebody is in such a state that she needs to be driven home, that is, I think, a very strong indicator that she may not be capable of consenting," said Viktoria Kristiansson, a Philadelphia lawyer who advises the Washington-based group AEquitas: The Prosecutors' Resource on Violence Against Women.
Attorney General's Office staffers will be examining the credibility of the accused and the accuser, Kristiansson said. It would be hard to believe - and perhaps easy to convince a jury of this - that the accuser would make up her story, Kristiansson said.
The original charges flowed from an October office party at a restaurant in Blue Bell after Kerns learned that the alleged victim feared she had consumed too much alcohol to get behind the wheel of a car. Prosecutors alleged that Kerns offered her a ride and, once in his car, gave her wine that he had spiked with Ambien. After that, he sexually assaulted her twice, authorities said.
Authorities believed the report of the analysis concluded that Ambien was in her system. Actually, it found none of the drug.