The U.S. Supreme Court ruled in Melendez-Diaz, that a forensic lab report could not be used against a criminal defendant unless the analyst that prepared the report also testified and was subject to cross examination. The Court essentially reaffirmed the principal from Crawford v. Washington, 541 U.S. 36 (2004), which held that evidence, such as affidavits, was "testimonial" in nature, and that a defendant has the right to cross-examine the maker at trial.
After the "Crawford" decision was handed down, the N.C. General Assembly passed what has been termed the "Anti-Crawford" statute, N.C. Gen. Stat. s 20-139.1. Under the current version, a sworn officer's or chemical analyst's documentation regarding a defendant's alleged blood alcohol concentration (BAC), was automatically admissible into evidence, even if the preparer was not in court. This hinders an ability to defend a client because there was no way to verify that the document submitted to the court was the actual one prepared for this client, and there is no way to cross examine the officer/analyst on the techniques used to ensure that the proper procedures were followed.
The statute did allow for the defendant to subpoena the analyst, but defense attorneys have to jump through several hoops to get them in court. The Melendez-Diaz decision (although it arose of of New Jersey), has already started having an impact in North Carolina. The General Assembly is currently in the process of revising the statute to require the "prosecutor" to give the defendant notice that they intend to use a document, and if the defendant objects, then the officer or chemical analyst must be brought to court by the State. This shifts the burden to the prosecutor to prove their case, rather than the defendant trying to disprove the State's.