For decades, police officers have used field drug tests while detaining suspects to determine whether a substance is an illegal narcotic. These tests are inexpensive, costing roughly $2 each, and are seemingly easy to use. In most field tests, a police officer deposits a portion of the substance in question into a vial of pink liquid. If the liquid turns blue, the substance is considered to be an illegal drug. While these tests are not admissible in court, law enforcement agents often use these tests as evidence to support an arrest.
Unfortunately, however, these tests are problematic for many reasons, the biggest being the issue of false positives. According to a recent New York Times Magazine article entitled, How a $2 Roadside Drug Test Sends Innocent People to Jail, labs across the United States have found disturbingly high rates of false positives in field drug tests.
There are many potential reasons for these errors. For example, many police officers are not properly trained on how to conduct these tests. In addition, certain types of chemicals, such as household cleaners or acne medication, can create false positives. In the end, however, it doesn't matter how the errors occur. False positives in field drug tests can unjustifiably wreak havoc on a person's life.
Nevertheless, police officers often use these tests to justify an initial arrest, and even if a person is later exonerated, the humiliation and anguish of an unjustified arrest is a major infringement on a person's rights. In the worst case scenario, the results, (often false) may be used to gain leverage over a defendant in an attempt to extract a guilty plea.
Field drug tests are not admissible in court and in fact, defendants have protections against these these types of tests. In Massachusetts, for example, any substance being evaluated to be an illegal drug must be tested in a licensed laboratory. Furthermore, it is no longer permissible for the prosecution to merely introduce a lab certificate to prove that a substance is in fact an illegal narcotic. Instead, defendants have the right to cross-examine the lab technician who performed the test. The United States Supreme Court case of Melendez-Diaz vs. Massachusetts confirmed this right.
The many issues and problems surrounding these types of tests in connection with a drug arrest highlight the critical necessity of a person accused of a drug crime to retain the services of a knowledgeable attorney.
Sources: How a $2 Roadside Drug Test Sends Innocent People to Jail, The New York Times Magazine, By Ryan Gabrielson and Topher Sanders, Melendez-Diaz v. Massachusetts, 557 U.S. 305 (2009)