In regard to DNA evidence here, there’s 4 main possibilities as I see it:
They have a perfect sample, and know it came from the suspect (unlikely, as I think we’d have a firm DNA generated description of him).
They have a perfect sample, but don’t know it came from the suspect (quite possible).
They have a sample, but it’s of low quality (I think this is most likely).
They have no DNA from anyone who could be involved (unlikely).
Blood DNA tests to tell someone's age someone's age - Business Insider
https://www.businessinsider.com/its-now-possible-to-tell-someones-age-from-blood-at...
Jun 30, 2016 - Until now, blood DNA tests could determine someone's ethnicity and sex, ... test that can be used at a crime scene to determine someone's age ...