Unfortunately Mangum's statement unrebutted by the defense is probably is a prima facie case then. While you are correct, the rape exam is about was weak as it can be, it does not show that a rape could not have taken place.
What is going to do Nifong in is his refusal to look at the evidence the defendant's offered him or Roberts throwing him under the bus and admitting he gave her the sweatheart bail deal in exchange for her moving her story toward Mangun's.
No, you're not understanding. In order for there to be a prosecutable case, the first thing required is that there be an objective, substantiated showing that a crime occurred. Such a showing, which derives from evidence, is unrebutted due to there being no evidence that conflicts or rebuts it. That is determined at the investigative phase before there is a defense. It's not something the defense presents, but is part of the process of determining if a crime was committed and, if so, what crime. The conflicting statements, which are evidence, along with Kim's statements are dispositive of a crime having occurred.
The rape exam and the lack of DNA foreign to Mangum or anybody she admits having consensual sex with are also dispostive of a crime occurring. The reason the rape exam is dispositive of the crime occurring is because Mangum describes be anally assaulted, beaten about the head and face, kicked, and held in a choke hold. There is no physical evidence of any of that occurring, so the medical report is inconsistent with the accuser's statement. Further rebutting her accusation is photographic evidence of Mangum falling down the steps and having bruises on her legs at the outset of the dancing. The fact that it's the defense that has that evidence is beside the point. It exists, and was offered to the prosecutor who declined to look at it. That means the prosecutor refused to look at evidence that directly pertains to whether or not a crime occurred at all.
What has happened here is that Liefong has defied the accepted presumption that LE's job is to investigate crimes and alleged crimes with due diligence for the purpose of attaining a just result. There is nothing failsfe in NC's system - no check and balance - to address a situation in which the steps taken by LE deliberately avoid the expected and presumed purposes of diligent officers engaged in the criminal justice system.
The reason I think her statement might not be enough is because there isn't enough support for the specifics of her statement. The physical evidence doesn't back up her story. She'd get on the stand and testify to a brutal gang rape in a small space. She got penetrated anally, vaginally and orally. No one used a condom and two of the guys "finished". Then the medical personnel will testify that they found edema and two cuts. The only semen they could find was her boyfriend's. Her story doesn't match the facts. None of her stories match the facts.
If just her story is enough then any woman can claim rape by any man and even though there are no injuries or evidence of any kind other than her say-so, the case can go to a jury. That doesn't seem right to me. That may be the law but if so, then Shakespeare was right - the law is an ass.