Each side presents evidence in light most favorable to them.
You can't look at just prosecution or defense evidence in a vacuum. Particularly in a motion.
I'm going to guess that the DNA evidence has some tie to Shannon or else the defense would be admitting it themselves. They are probably trying to argue that the presence of other male DNA makes the sample unreliable. I'd do the same thing.
It's not likely to work though. The judge will likely just say, that's why you have a DNA expert, to allow you to argue to the jury that the presence of other male DNA creates doubt.
But of course I'm also just making a guess, albeit one with a wee bit of experience, still just a guess.