I have to agree with Scalia. The victim's statements were not in the nature of a "dying declaration" as the victim had no clue that he was about to die. The police were interrogating the victim and were not in the least concerned with his imminent demise and the factual set up by the police in this case was clearly a ruse designed after the fact to make the victim's testimony appear to fall within the dying declaration exception to the hearsay rule.
The court should simply have stated that the facts did not support the dying declaration elements and then it would never have created this new fluid definition of the confrontation clause that weighs the seriousness of the crime against the constitutional protections for the confrontation of witnesses.
The rule has always been that a dying declaration is one in which the declarant believes he is about to die. This case did not fit those facts.