Confrontation confrontation

What are the full limits of confrontation when it comes to scientific and expert testimony.

Federal evidence blog notes:

In denying certiorari review (this week0 in eleven cases raising Confrontation Clause and expert testimony issues, for the foreseeable future the Supreme Court will not resolve a significant issue that has been dividing the lower court; it remains to be seen when the guidance urged by the lower courts will be provided.

They further note that a twelfth case will be considered in June. A Conference is set for June 5, 2014, in the twelfth case: Derr v. Maryland (No. 13-637), which presents the following issue:

Whether the Sixth Amendment permits the State’s expert witness to present to a jury the results of forensic tests that she neither performed nor witnessed as substantive evidence to support her conclusion that Petitioner was the source of DNA evidence, when the State does not call the analysts who performed the tests as witnesses or show that they are unavailable and previously subject to cross-examination. As the Petition For A Writ Of Certiorari summarizes:

This case concerns an important question of constitutional law that is frequently litigated in criminal cases: the limits the Confrontation Clause places on the government’s use of an expert opinion that is based on the results of forensic testing that have been made known to the expert but about which the expert is not competent to testify. The Court sought to answer that question in Williams, 567 U.S. __, 132 S. Ct. 2221, but the divided decision has spawned enormous confusion, and deep conflict, in state and lower federal courts. This case provides a proper vehicle for the Court to provide authoritative guidance to the lower courts because the decision in the court below is in conflict with the decisions of at least eleven state supreme courts and three federal courts of appeals.