The guy initially "cooperated" and answered questions and, at a certain point, finally just shut up and refused to speak anymore. It was ruled that the fact that he suddenly decided not to "cooperate" and became silent could be used against him.
I imagine the state arguing it to the jury similar to this: "Mr. Doe was helpful and cooperative at first and happily answered our questions. Then, when we asked him about <insert crime here> he stopped being cooperative and refused to answer any more of our questions. If he wasn't involved with <the crime>, why wouldn't he continue to cooperate?"
