well, i’ve helped gather evidence from an accused in the er before; combing the chest and pubic hair, swabbing the penis, and scraping under the nails. Of course, this is searching for bits of the victim, not dna of the alleged perp. In this case if they are uncooperative they get held down by as many cops as needed, hog tie retraints, anti-spitting hoods, what have you. i’m not sure what the legal requirements are, but time is a factor, and I never saw a warrant as such.
I’m not disputing that other DNA was found, but just how do they know what his intent was? Maybe he likes giving gay oral sex. That it confuses the DNA test hardly proves it was intentional.