Melendez-Diaz Ruling Tangles US Drug and DUI Prosecutions Nationwide

The US Supreme Court case of “Melendez-Diaz v. Massachusetts” is seen as a huge victory for criminal defense lawyers, and one that could cause headaches for state prosecutors across the country.

bag of weed
Creative Commons License photo credit: D.C.Atty

In the past it’s been a common practice for prosecutors in drug possession cases to submit a “drug certificate”, a document signed by a state forensic drug recognition and analysis expert certifying that the substance in a given criminal case is indeed an illegal or controlled substance.

This decision changes that commonly accepted standard of evidence, and requires that prosecutors provide testimony from a live witness who certified the evidence.

The issue revolved around the US Constitution and the 6th Amendment right to “confront one’s accuser”. Defense lawyers argued that one couldn’t cross examine a document, so there was no opportunity to challenge drug certificate evidence, and the Supreme Court agreed, in a 5-4 decision.

The practical impact of this decision is that most states only have a handful of forensic scientists and drug recognition experts who do this kind of work. To appear in court on potentially thousands of cases means an impossible workload without hiring a much larger team of experts able to travel to different courts and testify.

But until those experts are routinely available, defense attorneys may be able to get many drug cases easily dismissed, without the state required witnesses supporting the evidence to back up the charges of illegal drug possession.

Impact of Melendez-Diaz in Other Types of Cases

Now that this door has been opened, other types of criminal cases that use certification evidence are now being challenged across the county. Judges in DUI cases are getting frequent challenges to breathalyzer certification documents, and in many cases are either delaying trials or dismissing the charges.

The Governor of Virginia is calling for a special session of the state Legislature to deal with this issue. The likely result will be emergency funding for additional forensic experts to testify in these cases.

Other types of cases likely to cite the Melendez-Diaz ruling include automated red light cameras and speeding monitors that automatically photograph, scan, and issue citations through the mail to alleged traffic offenders.

We will keep an eye on legal developments and the practical implications resulting from this landmark case.


Forensics Guy accused prosecutors of “Whining” about Melendez-Diaz, and says forensic scientists who are called to testify will have to do a better job in both analyzing and explaining the results.

“It’s interesting to see prosecutors so worried about this ruling. Maybe not being able to misrepresent what the lab reports mean, with the actual lab analyst present, is a concern?”

About David Matson