Well the police want them because there’s a good chance that the numeric profile will help solve future crimes, e.g. arrested for but not charged with a minor scuffle in the street today, charged with a fraud in 2020.
My problem is that DNA evidence is regarded as the be-all and end-all of guilt, and may override other evidence. What happens when you sneeze in the tube, or have a spontaneous nose-bleed (which I do, occasionally) then the woman next to you gets raped on the way home. You’re miles away, but your DNA is there. Or a couple of hairs from your coat in the restaurant cloakroom get transferred to the one next to you?
Is DNA evidence overrated? Can some biochemist discuss?
I think there was a case in the 90s where a man was convicted of raping a friend on DNA evidence – yet SHE said it wasn’t him!