Michigan Police Consider Using a Portable Drug Test for Suspected Drivers – Is it Reliable?

When a police officer suspects a person is driving under the  influence of alcohol they will generally administer a preliminary breath test (PBT) at the site of the traffic stop. The results usually determine whether the suspect gets arrested. The PBT provides an objective and usually reliable breath alcohol content from which the officer will make an arrest decision. It is seen as a significant useful tool for DWI enforcement. But, the PBT only works with alcohol, not with drugs.

The use of medications that could possibly impair a driver is widespread. The increase of drug impaired driving, especially involving marijuana has prompted a demand for a roadside test for drug impaired driving suspects similar to a PBT. The newest tool currently being experimented with law enforcement all over the country is an Oral Fluid Collection device (OFC). An OCF is supposed to collect a saliva sample from a suspected driver and identify the presence of a drug. Proponents of these devices say that it is accurate and reliable as much as urine or blood. Others say the science has a long way to go before widespread use in law enforcement.

Just like a PBT there must be a waiting period before its use. This means the operator must wait at least 10 minutes between contact with the suspect and administering the test. The waiting period assures a pure sample without anything being placed in the mouth cavity immediately beforehand. Then, the device will collect a saliva sample from a suspect’s mouth with a long tube with an absorbent material at the end. The result is supposed to specifically identify a drug that was recently ingested by the subject. Some designs actually  produce a number corresponding to the concentration of the drug detected; others do not.

Unlike an alcohol PBT, the drug test will take up to 10 minutes to obtain a result. This is a significant amount of time. A PBT provides an immediate result. According to the Constitution, an officer may only detain a person for an investigation for a reasonable amount of time. Defense attorneys will surely argue that 10 minutes exceeds the amount of time that is reasonable. This issue demonstrates a certain flaw in this testing device.

The Draeger Drug Test 5000 may be the most popular OCF and is already in use in several cities including Los Angeles. It tests for seven types of the most commonly abused drugs. It utilizes competitive immunoassay technology which uses an antigen to detect the presence of the particular drug (antibody) tested for. The Drager uses absorbent test strips that contain the antibody. The saliva sample placed on the end of the strip. Each drug will be labeled so when the drug antibody binds with something it gives off a detectable color. If there is no drug present the sample will bind with a “conjugate” or alternative to the antibody and the strip will display a red line. This is the “competitive” nature of the science. The less the sample binds with the conjugate the more a drug is detected therefore creating an inverse relationship with the response.The instrument utilizes a LED light source as a detector. It will measure the amount of the color detected by the reaction.

The proposal seeks to purchase five devices at $6,000 each. Each test would cost about $25.