Ilya,
This is a fascinating thread topic and thank you for suggesting it. I'm not a judge, but I am an attorney, so I will take a stab at this. It occurs to me that it may be even MORE intriguing to ask the attorneys here to pick one side or the other and argue a case, in a truly lawyerly fashion (i.e. eliminating all personal and unsubstantiated opinions, unattractive personal attacks, and adhering to the strictest evidentiary standards. Any statement made must be thoroughly sourced and documented, etc.). I know that threads along this line have been proposed before but I don't know that the outcome was what I'm envisioning.
I have spent the morning furiously researching DNA standards (thank you, Helen, for the very helpful and informative link) and I gather that DNA evidence is, if properly gathered, indeed conclusive, absent the party who's contesting it bearing their quite considerable burden of proof to the contrary. At least for the purposes of this post, I will make that assumption (I'm not saying that I don't believe it to be true, but am qualifying it as an "assumption" because my research on this point is far from complete). So, despite the other forensic evidence to the contrary, I would have to rule that AA and AN were not the same person; that is, unless one of the attorneys before me were able to prove, beyond a reasonable doubt, that the DNA results were somehow rigged. (I think it has been shown through a number of very comprehensive discussions elsewhere in this forum that the DNA results do not, and in fact cannot, demonstrate that AA was FS, so I won't address that here.)
I would demand, given the decades-long notoriety preceding the disclosure of DNA results in this particular case (which indeed distinguishes it quite significantly from a typical DNA case), an impeccable and seamless history regarding the intestinal sample be presented to me and placed in evidence, including how the tissue specimen was obtained, where it was kept and for how long, how we can ascertain chain of custody at all points in time, and of course the credentials of and methods employed by the scientists conducting the tests. I would accept the forensic evidence apart from the DNA into evidence if it were presented in connection with a credible argument that the DNA was tampered with, but I could not use it as conclusive proof in light of the fact that DNA does trump the other evidence.
I would expect the moving attorney (i.e. the attorney bearing the burden of proof that the DNA was rigged) to demonstrate that somebody had the (1) motive, (2) opportunity, and (3) expertise to switch the tissue sample, and that that individual and/or his/her agents in fact (4) DID effect the switch. This is beyond my purview as judge in this matter, but I believe the moving attorney would have much evidence, at least based upon what I've learned, to demonstrate that a motive existed; and I would be willing, as judge, to entertain these arguments (indeed, would be obligated to), owing to the extraordinary history of the case. (I'm not going to get into a detailed discussion of specifically why I personally think that, because it would lead to a post of many pages and, in any event, is not I think what Ilya had in mind when he proposed this thread. I'm not supposed to be presenting a case here, right?!)
I would nonetheless be quite fascinated, should Ilya decide to permit somebody willing to take the role of "moving attorney" on this thread, to listen to somebody else's argument on this point! I would thoroughly enjoy it. Okay, now somebody who's a litigator or judge needs to step up to the plate. And I ask in advance for your leniency with respect to any glaring errors I've made.