I'm not trained as a lawyer, but I think the judge makes decisions regarding the admissibility of evidence, and for good reason often times. Juries then make decisions based on the evidence heard (that's why we have juries!).
btw, based on what i know about this case (which isn't a lot), i don't think he should have been convicted.
Exactly. Often juries' information is filtered by the judge in ways that defy common-sense.