Don't know if this subject has been covered as I'm unable to keep up. I've been thinking about the blood evidence and wondered about issues surrounding the hymen of a six year old girl. I found this link that answers a few questions (never thought about this subject at any length before).
http://www.ncbi.nlm.nih.gov/pubmed/12032529
The study was to determine what changes (in non sexually abused subjects) may occur by looking at girls between ages 3 and 5 and then again at ages 7 and 9. Few changes were noted.
I wonder what info, if any, during an autopsy might be obtained when examining the area or if the damage from the rape would cover up anything or conclude nothing had happened earlier. I assume the blood found on the garments was due to forcefully breaking the hymen but the rape may have caused other abrasions as well. So sad.
I had to read your post several times but I think you are wondering if there is a way to determine if previous sexual assaults or molestation occurred?
I don't know. My thinking is that a child rape would cause so much trauma to that area that they would not be able to tell the answer about the past. And docs do not check that area at well child visits, so...unless someone talks I doubt they will know that info.