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.
".....SBI lab was unable to determine, from the vaginal swabs,..."
Given that SBI touts the STR method on its website (posted earlier), they SHOULD have been able to. Here is a bit on STR methods I found elsewhere written in plain english:
For human identification purposes, it is important to have DNA markers that exhibit the highest possible variation in order to discriminate between samples. It is often challenging to obtain PCR amplification products from forensic samples because either the DNA in those samples is degraded, or mixed, such as in a sexual assault case.
The smaller size of STR alleles make STR markers better candidates for use in forensic applications, in which degraded DNA is common. PCR amplification of degraded DNA samples can be better accomplished with smaller target product sizes.
http://www.dna-forensic.com/dna-str.html