Children are the victims in more than half of the rape and gross-sexual-imposition cases filed against adults in Franklin County, Oh., says the Columbus Dispatch. Those cases are just a small fraction of the children who are sexually assaulted. The overwhelming majority of investigations don’t result in an arrest or indictment, in part because victims typically take so long to disclose what happened.

“Most of the cases that come to us are not fresh,” said Sgt. Mark Kaeppner of the Columbus Police Division’s Sexual Assault Unit. “They may be weeks or months or even years old. Any medical evidence that may have existed is gone. We lack DNA, we lack video, we lack actual witnesses to the abuse.” Jurisdictions across the U.S. have similarly low rates of prosecuting such cases, said David Finkelhor of the Crimes Against Children Research Center at the University of New Hampshire. “The issues that inhibit prosecution have to do with not all victims and their families being eager to participate,” he said. “And often (investigators) don’t have the elements they need to be confident of making the case stick.”