As a listener, this meant I honestly felt like I had wasted a huge amount of time on the show.
But I was rooting for them right up to the point at which I began cursing them.
That seems like such a weird conclusion to me.
So, many weeks later, when the final word was "gosh maybe we'll never know!", I felt like I'd clicked on a series of those "What happened next will shock you!" headlines.
A compelling story reaching the same conclusion probably could have been handled in a single episode.
But... that's the point. The finally episode spells this out very explicitly - although they can't say either way whether he did it or not, they found they don't have sufficient proof they he did commit the crime he was convicted for, and therefore does not deserve to be in jail.