Sotomayor's Majority Opinion

The Confrontation Clause of the Sixth Amendment provides criminal defendants the right to confront all adverse witnesses against him. In the opinion, the Court drew on the historical examination of the confrontation right that was seen in past cases, such as Crawford v. Washington, which stated that “the principal evil at which the Confrontation Clause was directed was the civil-law mode of criminal procedure,” which allowed the “use of ex parte examinations as evidence against the accused”. The Court in Crawford reasoned that, since the text of the Confrontation Clause did not allow the possibility of open-ended exceptions to the rule as determined by the courts, the Clause should be read as including only the exceptions that would have been present at the time it was written. To that point, the Crawford court argued that the Framers would not have allowed such out-of-court testimony to be admissible, unless the witness was unable to testify at trial and the defendant had a prior opportunity to cross-examine the witness.

Regarding the New York Court of Appeals decision in People v. Reid, the opinion rejects the appellate court's notion that the "door-opening" rule established in Reid is an exception to the Confrontation Clause. Rather, it asserts that it is merely a "procedural rule" dictating the manner in which a defendant may assert his confrontation right, and that it does not limit the scope of the right itself. The opinion rejects the notion that it was the responsibility of a judge to determine whether Hemphill's assertion of Morris's responsibility for the shooting was reliable, credible, or even that it had the opportunity to mislead the jury. It also rejected the notion that it was the responsibility of a judge to determine whether the admission of Morris's allocution was necessary in order to correct this misleading assertion.

The opinion rejects the State's assertion that the rule in Reid is necessary for courts to carry out their primary duty - to ascertain facts - by preventing the introduction of misleading evidence. While this task is important, the Court has never allowed this consideration to override the protections afforded to criminal defendants by the Sixth Amendment to the United States Constitution.

Lastly, the opinion contends with the assertion that a reversal of Hemphill's conviction would leave prosecutors without recourse to protect against the abuse of the confrontation right. Quoting Holmes v. South Carolina, the Court notes that “well-established rules” of evidence “permit trial judges to exclude evidence if its probative value is outweighed by certain other factors such as unfair prejudice, confusion of the issues, or potential to mislead the jury”.

Alito's Concurring Opinion

Alito's opinion begins with establishing the two modes by which a federally guaranteed constitutional right may be waived, either expressly or implicitly. Regarding the former, he states, quoting Johnson v. Zerbst, 304 U.S. 458 (1938), that waiver consists in the "intentional relinquishment or abandonment of a known right or privilege". Regarding the latter, quoting Berghuis v. Thompkins, 560 U.S. 370 (2010), he states that implied waiver can be established through “‘a course of conduct’” even “absent formal or express statements of waiver”.

Alito then addresses past cases in which a defendant's conduct has constituted an implied waiver of his Sixth Amendment right to confront adverse witnesses. As in Melendez-Diaz v. Massachusetts, 557 U.S. 305 (2009), implied waiver may be found in a defendant's "failure to object to the offending evidence". As in Illinois v. Allen, 397 U.S. 337 (1970), implied waiver may also be found in a defendant's “conducting himself in a manner so disorderly, disruptive, and disrespectful of the court that his trial cannot be carried on with him in the courtroom”.

Alito notes that the issue with the appellate court's rule in Reid is that its application in the case was predicated on neither an express nor an implicit waiver of the right to confront adverse witnesses. He does say, however, that there are instances where a defendant's introduction of evidence may amount to an implicit waiver of the right to object to the introduction of the prosecution's evidence that would otherwise be barred by the Confrontation Clause. One such instance relates to the doctrine of completeness. Federal Rules of Evidence #106 states:

If a party introduces all or part of a writing or recorded statement, an adverse party may require the introduction, at that time, of any other part — or any other writing or recorded statement — that in fairness ought to be considered at the same time.

He argues that this analysis is analogous to logic regarding the Fifth Amendment's privilege against self-incrimination. Precedent makes clear that defendants who waive their Fifth Amendment privilege against self-incrimination by testifying in their own defense cannot invoke that same privilege to avoid being cross-examined. In this example, such a defendant purposefully elects which details to disclose in his testimony, and so he cannot reasonably claim a constitutional immunity from being cross-examined on matters that he himself has put before a jury, and has thus deemed disputable. Alito argues that the right to confront adverse witnesses should be analyzed no differently, stating that a defendant's deliberate choice to place portions of statements of an unavailable declarant before the trier of fact (knowing that the declarant is unavailable for cross-examination) implicitly commits him to the trier of fact's examination of the entirety of what the declarant has to say on the subject.

Thomas's Dissenting Opinion

Thomas's dissent disputes the Supreme Court's jurisdiction over this case. Citing 28 U.S.C. § 1257(a), he indicated that the court may review final judgments from, in this case, the New York Court of Appeals only where a federal right "is specifically set up or claimed" in that court. Since Hemphill did not raise his Sixth Amendment claim in the New York Court of Appeals, Thomas claims that the Supreme Court lacks jurisdiction here to review the lower court's decision.