In drug cases the State has the burden to prove the substance they claim is a controlled substance is in fact what they claim it is. In other words, they have to prove the white powder in the baggie was cocaine. That is generally done by the forensic scientist - usually a chemist - who performed the tests. They will offer introduce their report, which is nothing more than a document statement what the substance is, and how much it weighs.
When I started practicing 30 years ago lab reports were routinely admitted; many times the lawyers would stipulate to admissibility, and the chemist might not even testify. Most lawyers at the time believed testing was pretty straightforward, and there was no reason to challenge it. That has drastically changed over the last few years. We now know that all sorts of errors can be made in testing, and sometimes the results aren't reported correctly.The only person who has knowledge of what was done - or not done - is the person who conducted the tests. Which means cross-examining that person is important.
Several years ago the Supreme Court issued an opinion in Bullcoming v. New Mexico which basically held that the lab reports were "testimonial", and they could not be offered with the testimony of the person who performed them. Relying on that decision, the Court of Criminal Appeals recently held in Burch v. State that the State could not use the supervisor of the lab in place of the person who actually did the tests.
The facts in Burch were fairly straightforward. Drugs had been to the Southwestern Institute of Forensic Sciences (SWIFS) for testing. A report was subsequently issued stating the material was cocaine, weighing 1.38 grams.When it came time for trial the analyst who did the testing was no longer working for SWIFS. Instead of trying to locate her, the State used the supervisor of the lab, and introduced the report through her. The Court held the State could not do that because it deprived the defendant of the opportunity to question the person who actually performed the tests.
It appears the recent failures regarding testing have had an impact on the Court. They clearly recognize that analysts do make mistakes, and sometimes blatantly disregard the procedures they are supposed to follow. Lawyers need to take notice also - and continue to vigorously challenge all evidence. When you do, sometimes good things happen.