I found this article very interesting:
Just little game of telephone could explain some of the mess.
Here's a relavent excerpt.
"This is what happens in sexual abuse cases all the time," observed Laurie Levenson, a former federal prosecutor who teaches legal ethics at Loyola Law School in Los Angeles. "Witnesses are embarrassed to describe in graphic terms what they saw and then it becomes a game of Telephone after that, as one witness changes the story a little before talking to the next witness."