i hear what you're saying, but i think you missed the point of my example. there is no question i am in possession of the picture, and they can trace where i got the picture from, but it would still be nearly impossible to find the girl in the picture with the way files get passed around the internet. which is why in cases like this they use pediatricians to determine the age of the girl, the same way that a voiceprint analysis expert is used in a trial to determine if a voice on a tape is that of the person in question, or a handwriting expert is used to determine if a signature is that of the person or a forgery. not everything in a case comes down to hard facts and indisputable proof, which is why experts are used to make determinations like this. then it's up to the judge or jury to decide.
and sofi, i think you missed my point as well. yes, with the girl in question and members of her family testifying that it isn't her on the tape, it would plant reasonable doubt in the jury's mind that it was THIS GIRL on the tape. but if it is determined that it is R. Kelly on the tape, and it is determined that the girl on the tape is underage regardless of who she is, then there should have been a conviction. after all, the law Kelly was accused of breaking was having sex with an underage girl, not having sex with this particular underage girl.