The question is, why should it pretend to be rooted in hard science if it's not?

If you're doing a mystery novel and not interested in the science, you'll handwave it: your detective will turn a sample over to the forensics lab, and the lab will come back with results that fit the plot, without explaining how they got there, just "this matches your suspect" or "well, we can tell it's a woman" or "we don't have a match for this."