Christopher Byers was the only boy whose body sustained genital injuries. The injury is technically called "degloving" in which the shaft of the penis remains in place while the surrounding tissue is stripped away. Defense experts, employed after the convictions for the appeals, have stated that the injury was caused by postmortem animal predation.
Perretti, the ME who performed the autopsy, stated that it was his opinion that the injury could have been caused by a serrated knife similar to one found in a lake behind Jason's trailer. However, no forensic evidence has been found on the knife found in the lake ("the lake knife") to link the young men in prison to the knife. Since the convictions, a witness (Joseph Samuel Dwyer) has testified at the Rule 37 hearing that he saw Jason's mom, Gail Grinnell, place a serrated knife in the lake well before the murders occurred.
I believe the defense experts, one of whom is the author of a textbook still used in forensic pathology classes today. The ME (who has never been able to pass his State licensing exam, even after multiple attempts) has been contradicted on several points by these recognized defense experts. The experts were not used at the trial because the defense counsels were young, inexperienced and underfunded.
I can see why someone would question why only one boy was "sexually mutilated" in this case. If this were the ritualistic Satanic attack the prosecution claimed, it seems reasonable that all three victims would have been mutilated. If the mutilation had been caused by the murderer, the question would then be, "Why was this victim singled out for this type of injury?" If, however, the animal predation theory is correct, it is much more easily explained.
IMO, for some reason Christopher's body was positioned in such a way that his genitals were dangling in the water. Alligator snapping turtles are known to be in the area, although none were found when the discovery ditch was drained. (That IMO is because police officers were in the ditch searching prior to the ditch being drained and that activity ran the wildlife off.) I have seen one report on the Internet about a man who was similarly injured by alligator snapping turtles while fishing. I think that alligator snapping turtles (or some other predator) caused this injury.
As you are new to the case, let me recommend a couple of websites to you for information. The Court documents are found at
http://callahan.8k.com/. Please be sure to read the transcripts of the pretrial hearings as well as the actual trials as the pretrial hearings reveal the amount of evidence excluded by Judge (now Senator) Burnett from the trial. The other website I would recommend is
www.wm3blackboard.com. This site is dedicated to finding justice for the three little boys as well as justice for the falsely-imprisoned young men. It is a very active discussion board.
Personally, I have been following this case since 1996, and I will be glad to answer any questions you may have. If I can't personally answer your questions, I can find the answer. I am a supporter of the innocence of the young men in prison.
There are also two documentaries available on this case, both from HBO. They are
Paradise Lost: The Child Murders at Robinhood Hills and
Paradise Lost 2: Revelations, both of which are available for viewing on youtube (in multiple parts) or for purchase through Amazon. Additionally, there have been numerous television specials on CNN, ID and other major networks that you can view through their websites. Most of these specials can also be viewed through the blackboard site I mentioned earlier. In addition, Aphrodite Jones is planning a special on the case on May 5, 2011.