It's a nostalgic look into the past to start with, an insight into the US that is no more, and is rarely seen on TV. The hair, the fashion, the rural rurality...:)
I love the fact that half of each episode is devoted to explaining how "luminol is a reagent that fluoresce in the presence of human protein" and "epithilial cells contain DNA from the mother", the repetition being an obvious artefact from the times when shows were aired once a week and you could not just binge-watch the entire series in a day...
Homicidal spouse always buys life insurance for the other half literally just before caving their skull in with a blender, it almost always IS the spouse who kills, and Peter Thomas deserves an Emmy just for the way he used to say "sentenced to life in prison, without the posibility of parole". 10/10 watch for long, lazy autumn evenings...:)