He lied constantly but the one fact is that he led the police to Hae's car. He's the only person with a clear connection to the case. I thought he did it throughout Serial until I figured he had little to no connection to her. The whole show left me uneasy about the courts. Adnan is the clearest suspect but there was practically zero evidence and the jurors they interviewed seemed to see their job as detectives instead of impartial peers.
And that seriously bothers me. He has some intense connection to it all, but what and 'it all' are a complete enigma to me. But that's absolutely it. I don't know if Adnan did it. That's such a hard thing to be certain on, but I came to pretty much the same conclusion and you and Sarah did: he shouldn't have been convicted on what they had. (I am a little more willing to believe he's not guilty, as well as be willing to admit that discrimination played a bigger role than she thought.)