Darius's confession without his attorney should have been admissible. 6th Amendment rights are offense-specific, and therefore, would only apply to the crime for which he had previously invoked his right to attorney (for the burglary). Thus, he would have to rely on his 5th Amendment Miranda rights; however, it was stated in the episode that he "signed a Miranda card", meaning that he waived those rights. So, neither the 5th or 6th Amendment would protect Darius in that situation.