The testimony of an alleged victim that she was raped is enough for a rape charge. If the DNA evidence comes back matching your brother, that is evidence they had sex. Then the only question is consent. If there is no DNA, the question is whether the DA will proceed based only on testimony and if so, will the jury believe it. If DNA matches someone other than him, then it seems clear that she had sex with someone else but blamed brother.
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The testimony of 1 eye witness to a criminal offense, if believed, is enough to charge, and even to convict someone of a crime in Maryland. There are exceptions to this general rule when the sole eye witness is a co-defendant, but that does not seem to apply here. Your question indicates that your brother has a lawyer. I think you should discuss your questions with him.
The fact that they had an ongoing relationship can help to explain why certain allegations were made. The lack of physical, and internal injuries is, or course, helpful. At the end of the day, the State is obligated to prove the case beyond a reasonable doubt, and all pieces of relevant direct, and circumstantial evidence will have an impact on the case.
Best of luck to you, and your brother.
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There is no magic formula for evidence. Jurors are instructed that they may believe all, some, or none of whatever evidence is presented. There is no way to predict what will convince a particular group of twelve people beyond a reasonable doubt or leave them with doubt. Fortunately, no one must prove his own innocence. The burden of proof is on the state. The possible verdicts are guilty and not guilty, because the evidence either meets the standard or it does not.
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