From a defense viewpoint, one of the highlights of Supreme Court jurisprudence over the last decade or so has been a trio of cases dealing with a defendant's Sixth Amendment right to confront the witnesses against him (or her).

In the three cases, Crawford v. Washington, Melendez-Diaz v. Massachusetts and Bullcoming v. New Mexico, the Court imposed and maintained stringent limits on a prosecutor's ability to admit forensic-type evidence while circumventing the Sixth Amendment's Confrontation Clause right to cross-examine. The actual evidence at issue in each of the three cases was different: Crawford (a tape recording), Melendez-Diaz (a state forensic laboratory report) and Bullcoming (a blood alcohol report).

But the constitutional principle was the same: defendants have a right to confront the government's witnesses and cross-examine their testimony.  In other words, you cannot just admit into evidence a paper report or an affidavit, the government needs to produce a speaking witness who can be cross examined about the report.

This makes perfect sense. Live courtroom confrontation is the essence of the Confrontation Clause. It is a protection aimed at strictly prohibiting out of court testimony as evidence in a criminal case without the benefit of a defendant's cross-examination in order to test the evidence for viability and believability. 

What these cases have meant in practice is that in any instance in which the government seeks to offer any test or forensic examination, the test must be accompanied to the stand by the technician who performed it.  This technician will be subject to cross-examination on the proper handling and testing of the sample, or anything else germane to his direct testimony.

In Crawford, chronologically, the first of the three cases, Justice Scalia set forth a historical analysis of the Confrontation Clause and how it has been interpreted in the past, concluding that it properly applies to any "witness" against a defendant, meaning any person, statement or document whose purpose is to "bear testimony."

So, the state of the law seemed settled and was settled until this past June when the Supreme Court handed down Williams v. Illinois.  Apart from its ruling, the opinion is noteworthy for its somewhat unusual ideological lineup. Justice Alito wrote the majority opinion for a four-justice plurality, one of whom was Justice Breyer. Justice Thomas concurred in the judgment. Justices Kagan, Sotomayor, Ginsburg and Scalia dissented.

The facts are these: the defendant Williams was convicted in Illinois for sexual assault, aggravated kidnapping and robbery in a state court bench trial.

One of the state's witnesses was a police lab forensic specialist who testified that her forensic analysis matched another one done by an outside vendor, a company called Cellmark. She also testified that Cellmark was an accredited laboratory and established a chain of custody.

The defense sought to exclude the portion of the testimony about the Cellmark report as hearsay.  The state argued that the evidence should be admitted because the Confrontation Clause had not been violated as the defendant had the opportunity to cross examine the expert who had performed the test that the Cellmark test matched.   In the end, the evidence was admitted and the defendant convicted.

The Alito opinion upheld the evidence's admission by differentiating Williams from Bullcoming and Melendez-Diaz. In those cases, forensic reports were admitted in order to prove the truth of the matters asserted therein. Here, the Supreme Court held, the Cellmark report was admitted for a different and more limited purpose of seeing whether it matched something else.  Justice Alito reasoned that the forensic reports in Melendez-Diaz and Bullcoming ran afoul of the Confrontation Clause because they were the equivalent of affidavits made for the purpose of proving a particular criminal defendant's guilt.  This was not the purpose of the Cellmark report, thus reducing the "prospect of fabrication" and allowing the Court to admit the test and distinguish Williams from the trio of cases discussed above.

So where do we go from here?  The trio of cases remains good law and should continue to apply in most instances.  But Williams increases the likelihood that some types of forensic evidence can be utilized via affidavit-type testimony instead of a live witness.  And from a defense perspective, that is a disadvantage.