Was the Adena Watson case ever solved? I saw the dvds on sale at a store and this question started bugging me. I never did watch the final two seasons of the series run. Too bad for me.

Nope.

You should read David Simon's book. There was a real analogue for that case. It wasn't solved, either.

I thought they knew who did, so ideally it was solved, but they did not have the evidence.

But the viewer is still never sure about it - in a later episode they mention, just in passing, that their one suspect (they guy they interogated in the box for a whole episode in season one) had passed away.

But I thought after the old man died they found some more cicumstantial evidence at his house or the barn.