I'm quite torn ... while I really like that a German production went ahead and tackles genre material ... the fact that it is as flawed as it can be and then some, did not escape me. But first things first, because this has quite some nice ideas overall and plays them out neatly. And the different approaches to season 1 and 2 are really well done.
But it all gets undermined by a few things. Cliches be damned, I could live with those and they are not so bad - well not as bad as the overall "acting". Don't get me wrong everyone involved in front of the camera (and I'm sure behind the camera too) is very likely a more than fine person. But the emotions they are able to bring to the project ... are almost nonexistent! Which is really a tough thing to overcome while watching this. I don't think I would be cutting them some slack if I'd say they are trying ... some may even feel that is being mean (an impression I would not like to emote).
A cast change from season 1 to 2 that is being adressed in a nice way, probably elevates this acting wise - at least a little but. Also in season 2 there is one "casting scene", that while annoying probably has one of the best performances by one of the jurors ... who sadly is not seen too much in the show overall! The main bad "guy" in season 2 (we finally get a face to hate) is quite over the top and walks a fine line ... I think she missteps more often than not, but that is for you to decide.
The second season also expands time wise which I reckon had to do with the success the first one might have had. It also has a bonus episode after the show apparently is over ... throwing mysteries at the viewer and checking which ones stick - no this is not the German/different version of Lost - though I reckon some may feel it is.
I was thinking of giving it a 5, because that total derived of feelings "acting" was hard to stomache ... but I went with a 6 instead, since I do like that they at least went there ... even if they did so stumbling rather than with confidence!