Are you LE or former LEO who's investigated even one double homicide?
It's easy to armchair quarterback how a homicide investigation goes or should be going. I imagine they're like snowflakes in that they're all snowflakes but each is unique. IMO
You don't have to be a LE or LEO to know how DNA works and how automatic it is for getting convection in court cases.
I'm saying if they find a suspect who's DNA matches the DNA found at the crime scene, that person is going to be arrested and charged IMMEDIATELY.