Not exactly. He could have heard before then, as I think he suggests in the film. Someone could have told him what kind of car it was, right? Seeing as he was out looking for it. Or am I getting the timeline wrong here? I thought he got away with it by implying he didn't remember how he knew but that he wasn't with the car, leaving it to be unlikely but not impossible.
I've seen all of the questions I have after watching asked in here I think. What a clusterfuck. Unlike Steven's lawyers i'm not so sure there wasn't any malice either. That Kratz guy for one, and his little helper. And that ex-boyfriend, whom I didn't trust from the get-go, which at the time I figured was to do with the Element shirt. But in later interviews, while they were searching, he seemed sketchy, as did the Halbach brother. They both seemed to hide smirks, and maybe they were just giddy to be on tv but I feel they know more about it.
This is obviously really speculative but like I said, the more substantive stuff has been mentioned already.
Edit: Someone mentioned how insane it is that the jury convicted these guys. My guess is that in court they were essentially given a dilemma: either the simpletons did it, or the government, in some form, did. This was of course a false dilemma, slyly emphasized by Kratz in his final remarks in court (when he alluded to how outlandish claims of evidence tampering were). The jury wasn't there to determine who did it, only to say if the suspect did. But I'm sure they felt that they had to side with one of the two, at some level. Does that makes sense?