I was agreeing with you right up to "thus".
Okay, I'll rephrase. :-)
Thus, the SBI lab was unable to determine, from the vaginal swabs, whether or not the accuser had unprotected sex recently.
Doesn't sound much better for the SBI lab, does it?
Hey, I could certainly be wrong, it sure wouldn't be the first time. I just don't see any other way to read it at this point.