But McCafferty also said he's puzzled why no one intervened in the alleged assaults.

"Why didn't somebody stop it?" he said. "You simply don't do that. ... It's not done."

Authorities charged Richmond and Mays on August 27, the same day Jefferson County's prosecuting attorney asked DeWine's office to take over the case.

In addition to the rape and "nudity-oriented material" charges, the teens also were originally charged with kidnapping. A juvenile court judge dismissed that charge in October, according to McCafferty and Nemann, Mays' attorney.

"My client asserts his innocence, and he looks forward to his day in court," Nemann said.

Nemann also said that prosecutors gave letters to three teens who testified at the early hearing, telling them they wouldn't be prosecuted if they testified about what they'd done. Attorney General DeWine previously told CNN that prosecutors offered no deals. It was not immediately clear whether Nemann and DeWine differed on the existence of such letters, or on their definitions of "deal."

Local authorities asked the state to take over to show that "everything that can be done in this case is being done," county prosecutor Jane Hanlin told CNN affiliate WTOV at the time.

"And if that means eliciting the help of these people from the attorney general's office, then that's what we want to do in this case," she said.

In addition, the FBI has offered "some technical assistance" in the investigation, said FBI spokesman Todd Lindgren in Cincinnati. He did not go into detail. Offering such assistance is routine, he said.

The case has been complicated by a lack of physical evidence -- the family did not report the alleged assaults until August 14. It also apparently hinges largely on witness statements, social media images and messages posted after the incident and possibly some information gleaned from cell phones seized by police. The family gathered many of the materials and delivered them to police on a portable computer drive, McCafferty told CNN.

Police have heard of a video showing the alleged attack, McCafferty said. But authorities don't have it or know whether it even exists, he said.

Police did seize several cell phones and iPads during the investigation, and "there was evidence on some of the phones," McCafferty said without elaborating.

The New York Times reported that a cell phone photo from that night shows the girl naked on a floor.

A special unit with the attorney general's office is examining the materials, McCafferty said. DeWine's office has declined to comment on evidence in the case.

Text messages posted to social networking sites that night, later retrieved and published by a crime blogger, seemed to brag about the incident, calling the girl "sloppy," making references to rape and suggesting that she had been urinated on, according to crime blogger Alexandria Goddard. CNN has not established whether that is true.

Goddard, a former Steubenville resident, discovered and preserved many of the messages, at least some of which are now in the hands of authorities. She first spotted the story in the small town's newspaper and started looking into the situation on a hunch that the highly regarded football team's members were getting special treatment at the expense of the victim.

"When I first came across the article, I just felt like -- because it was involving football players, and there is a culture there that football is very important -- that there was probably a little more to this story than what the local media was reporting," she told CNN on Thursday. "So I started doing my own research."

The case gained additional exposure this week when a group calling itself Knight Sec and saying it is part of Anonymous -- the loosely organized cooperative of activist hackers -- published a video purporting to show Steubenville students discussing the assault in joking tones.

In the video, a teenager makes joke after joke about the girl's condition, saying she must have died because she didn't move during one assault.

Anonymous and others in the video identified the teen by a name that doesn't match the two who were charged, but CNN cannot independently confirm his identity.

"Is it really rape because you don't know if she wanted to or not," the teenager says on the video. "She might have wanted to. That might have been her final wish."

Other male voices can be heard off-camera, laughing and talking about the alleged assault. McCafferty said he cannot say who shot that video.

"The subject in that video was interviewed. He wasn't charged," the chief told CNN. "The attorney general's office has all this. It appears to me after I watched the video he was intoxicated."

Anonymous has taken up the case, hacking a site dedicated to high school sports in Steubenville and separately publishing on one of its websites a trove of images, texts and accusations involving students, coaches and boosters. Those individuals have not been named or charged by authorities with any crime.

Anonymous says it is collecting detailed information about the personal affairs of football boosters and others in Steubenville who the group claims may have helped cover up the alleged attack. It's also planning a protest "to help those who have been victimized by the football team or other regimes."