Role of the "Matrix" in the DRE Program

The issue of the "Matrix" was significant in Judge Galloway's Maryland vs. Brightful, et al. opinion.

The "DRE Matrix" is a common focus of questioning by both prosecutors and defense attorneys in court. In my opinion and experience, defense attorneys in particular attempt to attach far too much weight to this simple tool.

The so-called "Matrix" is simply a reference tool, a chart, that the Drug Recognition Expert officer may refer to before, during, or subsequent to conducting an evaluation. The "Matrix" is also known as a "Drug Influence Signs and Symptoms" chart, or simply a "Drug Use Indicators" chart. It's analogous to the Periodical Table of Elements that a physicist may hang on the office wall, a chart of the human skeletal system that a physician may refer to, or a sentencing guideline chart that a judge may use.

The typical "Matrix" consists of headings across the top - the horizontal plane - of the seven DRE drug categories. The far left column vertically lists specific categories of effects, such as pupil size, vital signs, HGN, vertical gaze nystagmus, lack of convergence, and other behavioral effects. Some matrices include lists of specific substances included within a category of drug, normal ranges of vital signs and pupil size, methods of administration, and more. A so-called "completed Matrix" lists the expected effects by drug category. For example, in the box under the Central Nervous System Depressant heading, and to the right of HGN, the words "present" would be placed.

The "Matrix" was initially developed by retired LAPD Motorcycle Officer C. Doug Laird in the mid-1980's. Officer Laird was one of the four LAPD officers who participated in the landmark Johns Hopkins study of the DRE program in 1984. Doug created a chart solely to help him remember and separate the various signs and symptoms of the drug categories. Many other officers developed their own version of this reference chart. It wasn't until the early to mid-1990's that DRE students were taught to complete a matrix chart during the classroom phase of DRE training.

(For many years, I resisted supplying DRE students with ready made matrices of drug signs and symptoms. I was concerned that students would memorize a chart, rather than fully understand and commit to memory the material of the course. However, over time, many students entered DRE training with charts given to them by DRE's, certainly with the intention of preparing them for the rigorous DRE training. Unfortunately, many of those charts contained inaccuracies - still true to this day!)

Currently, student DRE's periodically complete matrices from memory during the DRE school, including during the certification phase of training.

The "Matrix" is a reference tool and nothing more. The "Matrix" doesn't make the decision of impairment or determine the drug-category for the officer. The DRE simply references the matrix to refresh his or her memory, and to make sure that he/she didn't overlook the involvement of other drugs. The "Matrix" contains only a very small portion of the information that the DRE student is expected to master. And of course the "Matrix" teaches nothing about the skills and attitude (affective domain of learning) that a DRE must master.