It’s an important question since there is no doubt that Melendez-Diaz is a very favorable decision for criminal defendants. It rejects a lot of arguments that lower courts had been using to find out-of-court statements non-testimonial and admissible against the defendant.
I think the best way to look at the impact of the decision, including its effect on current habeas petitioners, is to break up the possible situations into three broad categories: (1) criminal defendants who have not yet been convicted; (2) defendants who have been convicted but their case is now on appeal, i.o.w. the conviction has not yet become final as the direct appeal has not yet ended; and (3) criminal defendants whose judgments of conviction became final before Melendez-Diaz. This final category includes defendants who have filed habeas petitions.
I’ll go category by category below the fold.