She did not wash right away, therefore it would make sense that some DNA would be on her. Thinking about it, the bathroom would be a place that would have alot hair in it, especially on the floor.
I wonder if the lawyers refused to let their clients to give hair samples until they had the results on the hair sent to the lab for DNA testing first. But I don't understand why they couldn't just get the pattern from the exemplar and compare it to the DNA patterns they already have on the guys. I don't understand why they needed a hair sample. I would be very suspicious of this if I was representing one of these guys.