I hate to point this out, because all of us hope that SA in any form didn't happen to these girls. But don't forget that a sexually motivated offender may have interests/desires/goals that do not meet the legal definition of rape and may not leave DNA behind. For some of these individuals, it's sadism, not actual sexual congress, that's bound to sexual desire or completion. There is a subtype of pedophile (I'm not sure that the Delphi crime was specifically pedophilic but I think the point stands) called a "mysoped," these offenders experience sexual pleasure because of the torture and death of their victims. Their sexually motivated acts may not leave any DNA as they are expressing their urges not through rape but sexual mutilation, cannibalism, sexual use of objects, other bizarre paraphilias etc. I apologize for the graphic nature of this post but I think it bears pointing out that with young female victims and older male offender, the crime is typically overwhelming sexually motivated in some capacity. The Delphi crime might be the exception (and I honestly hope the girls did not have to experience any kind of SA before they died, it is horrible to contemplate). But when you try to find non-SA crimes against young girls/women you find that even without rape there is often sexually-directed violence that is a component of the crime.